| List of the INTEGRAL emails | |
| 2004 2005 2006 2007 2008 2009 2010 2011 2012 | |
| 2012 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#557 12 Oct. 2012 |
Manousakis et al. 2012 accepted in A&A have used numerical simulations to model the flow of the stellar wind in the highly absorbed sgHMXB IGR J17252-3616. They study the dependence of the absorbing column density on the orbital phase, and by comparing the simulations to observations allows them to constrain some of the source parameters. They obtain a mass of 1.75 to 2.15 solar masses for the neutron star and a wind terminal velocity of 500-600 km.s-1. This confirms previous conclusions of a slow velocity wind in this source All details in Manousakis et al. 2012 arXiV 1210.2952 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#556 8 Oct. 2012 |
Altamirano et al. 2012 accepted in ApJ report the results of their temporal
analysis of 6 RXTE observation of the 11 Hz pulsar IGR J17480-2446.
They find power spectra resembling those usually seen in Z sources with QPO in the 35-50 Hz range and a kHz QPO at 815 Hz. The main conclusion of their work is that the 35-50 Hz QPO cannot be, as was previously thought, be explained by Lense-Thirring precession since the pulsar in this object spins much more slowly than any of the other objects known to exhibit these kind of QPOs. All details in Altamirano et al. 2012 arXiV 1210.1494 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#555 18 Sept. 2012 |
Reis et al. 2012 ATel 4382 report the results of XMM analysis
of an observation of IGR J17091-3624.
The spectral analysis of these data shows the presence of a number of absorption lines and a distinct feature at 7.1 keV. They mention that a good fit is obtained with a photoionization model, as reported in previous studies, but insist on the fact that a relativistic iron line model provides a better improvement to the modeling. Their conclusion is that the system is probably in a soft intermediate state during this obs with a disk temperature 1.1 keV and a power law photon index 1.9. From the analysis of the broadened iron line they constrain the inclination to the disc to be less than62 degrees with an emissivity index Q<7.4. The inner radius is constrained to be <2.3GM/c2 which may implies a black hole with a spin a*>~0.9 in contradiction with recent results obtained by another team More results in Reis et al. ATel 4382 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#554 17 Sept. 2012 |
Rao & Vadawale 2012 accepted in ApJ report the
results of their analysis of simultaneous RXTE and XMM
observations of the BHC IGR J17091-3624.
They focus on a phase resolved spectroscopy of the rho-like type of variability seen in this source and try to understand the differences (especially in flux) with the only other source showing such variability pattern GRS 1915+105. Using standard spectral models for BH binaries in outburst the authors conclude that the source is a high inclination system (> 53deg) and that the low luminosity of this system can be explained only if the spin of the BH has a low (or even negative) value, in a distant and light (<5 Msun) BH All details in Rao & Vadawale 2012 arXiV 1209.2506 Karasev et al. 2012 Astr. Lett, 38, 629 report the results of Chandra/HRC and XMM-Newton refinement of the position of 5 IGR source and the subsequent counterpart and tentative source identifications. The main results are the following: IGR J18048-1455 is identified as a CV most likely an intermediate polar, IGR J12134-6015 and J17350-2045 are probable extragalactic sources, J18219-1347 is probably an HMXB. The counterpart to IGR J18293-1213 is found and the authors provide constraints on the type of the companion star for different values of the absorption on the line of sight. All details in Karasev et al. 2012 arXiV 1209.2945 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#553 10 Sept. 2012 |
The last The last IBIS catalogue by Krivonos et al. 2012 is now published in A&A (2012, 545, A27). The web site will be updated accordingly in the very near future. Bodaghee et al. report on the last X-ray observation of the field around IGR J17091-3624 performed on Sept. 6, 2012 with INTEGRAL. The source is found at fluxes 16 and 33 mCrab in the 18-40 keV and 40-100 keV energy ranges respectively. The spectrum is well fitted by a power law with Gamma = 1.6 with no evidence for a cut-off up to 200 keV. This confirms that a transition to the hard state has taken place. More details in Bodaghee et al. 2012 ATel 4360 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#552 29 August 2012 |
Rojas et al. 2012
ATel 4342 report on their search for IR counterpart
in the archival VVV survey.
The data in the Ks filter were acquired at different epochs permitting to check for variability.
The authors mention the presence of 10 sources in addition to the two
2MASS sources already mentioned elsewhere.
None of these show significant variability in the Ks band.
The authors cannot tell which (if any) of these sources is the quiescent counterpart to IGR J17559-2612 More details in Rojas et al. ATel 4342 Ricci et al. 2012 ATel 4345 report the discovery and Swift follow-up observations of 2 north pole IGRs: IGRJ02045-1156: Detected in the 17-80 keV range by IBIS/ISGRI with a significance of 5.6 sigma. A faint source is detected by Swift/XRT at: RA=31.15306= 02h 04m 36.7s DEC=-11.99501= -11deg 59' 42.0" (+-2.1 "). Ths position is compatible with the Seyfert 1 AGN 6dFGS gJ020436.8-115943 and that of the X-ray source 1RXS J020436.8-115941. The XRT spectrum is well described by a power-law model with fixed the absorption column density (N_H=1.8E+20 cm-2), and Gamma=1.6, compatible (within the errors) with the value Gamma=2 measured with ISGRI. IGRJ02574-0303: Detected in the 17-80 keV by IBIS/ISGRI at a significance of 5.8. A single faint source is detected with Swift/XRT at: RA=44.34122=02h 57m 21.9s DEC=-3.10622=-03deg 06' 22.4" (+-2.5"). No obvious catalogued counterparts in the optical and IR domain are found within the XRT error circle. The source is too weak for a meaningful XRT spectrum to be acquired. The ISGRI spectrum is well described by a power-law with Gamma~0.6. More details in Ricci et al. 2012 ATel 4345 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#551 21 August 2012 |
In ATel 4322, Bozzo et al. report the Swift refined position of the
recently discovered transient IGRJ17559-2612.
A single source is detected within the INTEGRAL error circle at:
RA= 268.9915 (17h 55 57.96s) DEC= -26.2300 (-26d 13' 48.0") (+- 3.6 arcsec). The XRT spectrum could be well described by an absorbed power-law model with Nh~6.0E22 cm-2 and Gamma~1.4 (with large uncertainties on both parameters). The authors do not find any optical counterpart and, however, mention that the closest catalogued 2MASS objects are 2MASS J17555833-2613457 and J17555783-2613530 that lie just outside of the XRT error box. All details in Bozzo et al. ATel 4322 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#550 20 August 2012 |
Pahari et al. 2012 ATel 4282, 4283 report on X-ray activity
of the black hole candidate IGR J17091-3624 since february 2012 (as
seen with Swift).
The whole summary is available in
ATel 4282
Esposito et al. 2012 ATel 4309 report the discovery of a new source
with IBIS (IGR J17559-2612) at RA= 17h 55m 58s Dec= -26d 12' 36" (+-3.5 arcmin). The spectrum can be fitted with a powerlaw with Gamma=1.6 All details in ATel 4309 Nowak et al. 2012 accepted in ApJ report the results of their X-ray (Chandra, Swift) and near infra red observations of IGR J18179-1621. They give the most precise X-ray position (RA= 18h17m52s.18, DEC = -16deg 21' 31.6", +-0.6") and present the results of the spectral and temporal analysis of the X-ray data. They detect an IR counterpart consistent with 2MASS J18175218-1621316 and give the magnitudes. They conclude that the source is rather unusual and does not clearly fit into an existing category of X-ray binary. More details in Nowak et al. 2012 arXiV 1208.0004 Falanga et al. 2012 accepted in A&A report the results of their spectral and temporal analysis of IGR J17498-2921 (including the X-ray bursts) as obtained with Swift, RXTE and INTEGRAL. The authors in particular remark that the profile of the short bursts indicate an hydrogen-poor material at ignition. This may suggest that either the accreted material is hydrogen-deficient, or that the CNO metallicity is up to a factor of ~2 higher than the solar one. They also mention that the variation in the burst recurrence time as a function of the accretion rate is smaller than predicted by helium-ignition models. All details in Falanga et al. 2012 arXiV 1208.1384 Girish & Singh 2012 accepted in MNRAS, report the results of XMM and Suzaku observations of the X-ray counterpart of IGR J17195-4100. They find a new period of 1053.7\pm12.2 s (~17.5 min) in X-rays, while a new period of 3.52 h (interpreted as the orbital period of the system) is strongly indicated in the power spectrum of the time series. They also report the results of their spectral analysis of these data. They in particular conclude to the possible presence of a variable partial covering accretion column/ All details and discussion in Girish and Singh 2012 arXiV 1208.3045 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#549 24 July 2012 |
Malizia et al. 2012, accepted in MNRAS present the most recent catalogue of AGN seen by INTEGRAL, a large number of which are IGRs. This catalogues lists 272 sources for which secure optical classification, redshift and X-ray properties. In this version the authors mainly study the absorption properties of their sample and test AGN unification scheme. All results and details in Malizia et al. 2012 arXiV 1207.4882 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#548 20 July 2012 |
Bozzo et al. 2012, accepted in A&A, report the results of XMM-Newton
observations of 5 sources amongst which 4 are IGRs.
They refine the positions for two sources to: IGR J08262-3736: RA=08h 26m 13.7s dec=-37deg 37' 11.58" (+-2") IGR J17348-2045: RA=17h 34m 58.80s dec=-20deg 45' 30.96" (+-2", favoured X-ray counterpart). They provide the results of the X-ray analysis for all sources, and discuss the type of the object. J08262-3736 is typical of a supergiant HMXB, while J17354-3255 (for which they conclude that only one of the two X-ray sources is the true counterpart), and J16328-4726 are SFXTs. In the case of IGR J17348-2045, the source is highly absorbed (Nh=1.7e23 cm-2) has a photon index Gamma=1.5. The close by radio object NVSS J173459-204533, if associated to the source, would suggest that it is an absorbed AGN. All details in Bozzo et al. 2012, arXiV 1207.3719 Li et al. 2012 accepted in MNRAS, report the results of Swift and INTEGRAL observations of IGR J18179-1621. They confirm the detection of a 11.82s pulsation, with a pulse fraction of 22%. Their spectral analysis reveals the presence of an absorption feature at 21.5 keV in addition to an absorbed (Nh=12.3e22 cm-2) cutoff power law (Gamma=0.59, Ecut =9.97 keV). The value of the absorption line, attributed to a cyclotron resonant scattering feature, implies a magnetic field B~2.4e12 G. The source is an accreting pulsar. More details in Li et al. arXiV 1207.3989 Very similar results are reported in Bozzo et al. 2012b accepted in A&A. The authors conclude that the object is an HMXB, either a supergiant or Be one. All details in Bozzo et al. arXiV 1207.4557 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#547 13 July 2012 |
Molina et al. 2012, ATel 4250 report the results of XMM observations
of 2 unidentified hard X-ray sources, one of which being IGR J17348-2045.
An object is detected in the XMM observation at RA = 17h 34m 58.89s Dec. = -20d 45m 31.0s (+- 5" assumed). USNO-B1.0 0692-0466331 ( R~17, B~19) also listed in the 2MASS catalogue (J=10.5, H=9.4 and K=9) is found within the XMM error box. This object is also a radio source (NVSS J173459-204533) with a F_{20 cm}=13.2 mJy. It is reported in the WISE catalogue with W1=8.73, W2=8.75, W3=7.46, W4=4.85. The source location (l=5.681, b= 6.37) its radio detection suggest that it is an AGN. The authors further suggest that IGR J17348-2045 is a probable Blazar. More details in Molina et al. 2012 ATel 4250 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#546 11 July 2012 |
Masetti et al. 2012,
ATel 4248 report the results of optical
spectroscopic observations of the putative optical counterpart
of IGR J22534+6243.
The spectral continuum is highly reddened, intrinsically blue with superimposed Halpha, Hbeta and He I emissions at redshift zero (plus several absorption lines). This is typical of an absorbed HMXB which confirms the HMXB nature of this source. More details in Masetti et al. 2012 ATel 4248 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#545 9 July 2012 |
Halpern , ATel 4240 report the detection of 46.6s
pulsations in IGR J22534+6243.
He found that the source was serendipitously detected with
Chandra at a position consistent with that of the previously suggested
IR counterpart.
Halpern report the detection of a 46.673 pulsation in all Chandra observations, and the pulsation is also present in the Swift data although at a slightly different period. The source is suggested to be a reddened HMXB More details in Halpern ATel 4240 Further to that Israel et al. 2012 ATel 4241 also report detection of pulsations at 46.6610s in the Chandra data. The authors also mention the presence of the pulsation in the Swift data, and report the detection of this pulse signal at 46.406s in archival (1993) Rosat data. They thus infer a preliminary period derivative of 5e-10 s/s More details in Israel et al. 2012 ATel 4241 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#544 6 July 2012 |
Landi et al. 2012, ATel 4233 report on the Swift archival
observations of 2 new IGRs from the Krivonos' catalogue IGR J16181-5407: A hard soure located at RA= 16h 18m 08.02s Dec = -54d 06m 09.8s (+-6 ") is detected. Three USNO-B1.0 sources, USNO-B1.0 0358-0591958, USNO-B1.0 0358-0591923 and USNO-B1.0 0358-0591979, having counterparts in the 2MASS catalogue are detected in the Swift error box. IGR J17157-5449: This source is also dubbed 2PBC J1715.2-5448 and identified as the star HD 155573. 1 X-ray source located at RA = 17h 15m 37.39s Dec= -54d 50m 04.5s (+-4.3") is detected by XRT. The XRT spectrum is well fitted with a power law having NH_Gal= 1.25 E21cm-2 and Gamma ~1.5. The X-ray position is compatible with that of the bright ROSAT source 1RXS J171535.6-545015 and that of the Einstein Slew source 1ES 1711-54.7. The XRT position rules out the association between the star HD 155573. The X-ray source appears as a blend of two distinct objects, both detected above 3 keV. The authors provide tentative positions and counterparts for these 2 sources, and conclude that since both have comparable fluxes they both contribute to the high energy emission seen by IBIS and BAT. More details in Landi et al. 2012 ATel 4233 Riggio et al. 2012 accepted in ApJL report sub arsec localisation of IGR J17480-2446. To obtain this high precision position, they use RXTE and lunar occultation of the source All details about the method, the resultant position of the source and discussion can be found in Riggio et al. arXiV 1206.4878 Farinelli et al. 2012 accepted in MNRAS report the results of Swift observations of the two 'prototypical' SFXTs XTE J1739-302 (IGR J17391-3021) and IGR J17544-2619. For both source they present the results of fits of the broad band spectra with physical models. They discuss the results in the context of Comptonization. More details in Farinelli et al. arXiV 1205.7059 Wang & Chang 2012 accepted in A&A present an alternative mechanisms retrograde wind accretion to explain the large values of the spin periods detected in a number of SFXTs. All details can be found in Wang & Chang arXiV 1207.1180 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#543 29 June 2012 |
Sugimoto et al. 2012, ATel 4170 reported renewed activity from the neutron star XRB IGR J17191-2821 seen with MAXI. The source was undergoing the first episode of outburst since 2007 All details (and links to light curves) in Sugimito et al. ATel 4170 Simon et al. 2012, ATel 4172 report the detection of reappearance of a decretion disc in the system IGR J06074+2205. This result was obtained with optical observations while performing spectroscopy of the source. The identification of H-alpha emission line and its V/R variability lead the authors to conclude that the equatorial disk has re-appeared. More details in Simon et al. ATel 4172 King et al. 2012 ATel 4173 report on the results of the last Swift observation of IGR J17091-3624. The source is still active and clearly detected. The best fit of the spectrum is obtained with absorbed power law + black body models. More details in King et al. ATel 4173 Rau et al. 2012 ATel 4214 report the results of GROND observations of the optical/NIR counterpart of IGRJ17062-6143. They report the magnitudes obtained in several bands All results in Rau et al. 2012 ATel 4214 Degenaar et al. ATel 4219 report the analysis of Swift observations of IGR J17062-6143. The observations and analysis of a ~200s broad peak lead them to conclude that this event was due to a thermonuclear X-ray burst. Further discussions and considerations lead them to conclude that the source is a neutron star LMXB All details in Degenaar et al. ATel 4219 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#542 13 June 2012 |
Some new IGRs were announced in a paper submitted by Krivonos et al.
(2012, arXiv:1205.3941), and there have already been attempts to
classify them.
Parisi et al. (2012) associate IGR J05470+5034 with SWIFT J0547.4+5042
which was detected by the Swift-BAT. The Swift-XRT also detects this source
in the 0.3-10 keV band at a position of ` R.A. (J2000) = 05:47:14.76 Dec. = +50:38:24.4 with an uncertainty radius of 5 arcsec. This position is compatible with that of 2MASX J05471492+5038251 whose optical spectrum suggests a Seyfert 2 galaxy at a redshift of 0.036(1). Details can be found in Parisi et al. (2012, ATel #4151) ATel 4151 Landi et al. (2012) announce likely Swift-XRT counterparts for 3 new IGRs. The XRT counterpart to IGR J14091-6108 is located at R.A. = 14:08:46.34 Dec. = -61:07:55.5 with an error radius of 4 arcsec. This error circle encompasses two optical sources: USNO-B1 0288-0488487 and USNO-B1 0288-0488489. The X-ray spectrum is hard (Gamma~1.3) with a column density equivalent to that expected along the line of sight (2e22 /cm2). The observed flux in the 2-10 keV band is 2e-12 erg/cm2/s. IGR J14257-6117 (= SWIFT J1424.8-6122) has an XRT counterpart at R.A. = 14:25:07.70 Dec. = -61:18:58.5 with an error radius of 3.7 arcsec. This position is compatible with USNO-B1 0286-0489119 (= 2MASS J14250758-6118578). The X-ray spectrum can be modeled with a hard power law (Gamma~0.95, and nH~1.7e22) that includes a low-temperature blackbody component (kT~0.1 keV). The source flux observed in the 2-10 keV band is 4e-12 erg/cm2/s. For IGR J22534+6243, an XRT counterpart is detected at R.A. = 22:53:55.23 Dec. = +62:43:38.0 (3.5 arcsec uncertainty). This position is compatible with the faint, unidentified ROSAT source 1RXS J225352.8+624354, and with USNO-B1 1527-0428738 (=2MASS J22535512+6243368). Modeling the X-ray spectrum requires an intrinsic absorption component (nH~1.1e22) in addition to that expected along the line of sight (9e21). The photon index is 1.4 and the observed source flux (2-10 keV) is 3e-12 erg/cm2/s. The source properties suggest a Galactic origin for all three objects. Please see Landi et al. (2012): ATel 4165 and ATel 4166 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#541 13 June 2012 |
Paizis et al. (2012) report on a 20-ks Chandra grating observation of the accreting millisecond pulsar and LMXB burster IGR J17511-3057. They determine the most accurate X-ray position available as R.A. (J2000) = 17:51:08.66 and Dec. = -30:57:41.0 with 0.6 arcsec uncertainty at 90% confidence. A type-I X-ray burst is detected at an average luminosity (0.5-8 keV) of 1.6e37 erg/s. The X-ray spectrum during this 54s burst can be modeled with a blackbody of temperature 1.6 keV (on average), but this temperature varies from 2.5 keV at the peak of the burst to 1.3 keV at the tail while the relative size of the emitting region (5 km) does not change significantly. For more, please read Paizis et al. (2012, accepted in MNRAS): arXiV 1206.2213 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#540 13 June 2012 |
Tomsick et al. (2012) propose Chandra counterparts for 14 of 18 unclassified IGR sources situated near the Galactic Plane. For these sources, we provide spectral information in the soft X-ray band (0.3-10 keV) and coordinates with sub-arcsecond precision. Four objects are confidently associated with AGN (IGR J01545+6437, IGR J15391-5307, IGR J15415-5029, and IGR J21565+5948) with an additional four AGN candidates (IGR J03103+5706, IGR J09189-4418, IGR J16413-4046, and IGR J16560-4958). Four objects appear to be Galactic in origin (IGR J12489-6243, IGR J15293-5609, IGR J16173-5023, and IGR J16206-5253), but only IGR J15293-5609 is confirmed as Galactic source (likely a symbiotic binary) given the previously-reported parallax measurement (1.56+-0.12 kpc) of the optical counterpart to the unique Chandra source inside the ISGRI error circle. More information, including Chandra positions and optical/IR SEDs can be found in Tomsick et al. (2012, accepted in ApJ): arXiV 1206.1071 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#539 5 June 2012 |
Altamirano & Strohmayer (2012) report the discovery of low-frequency QPOs in the accreting black hole candidate IGR J17464-3213 (= H1743-322). A QPO around 11 mHz is detected in RXTE and Chandra observations of the source at the beginning of its outbursts in 2010 and 2011 (and not during any previous outbursts). Given the similar hardness and intensity of the source when the QPO was detected, the authors suggest that the appearance of the QPO is related to the accretion state of the X-ray source (and perhaps to the presence of radio jets). For more information, please see Altamirano & Strohmayer (2012, accepted in ApJL): arXiV 1206.0476 In ATel #4148, Romano et al. (2012) report that the SFXT named IGR J16418-4532 has been detected in outburst by Swift-BAT (at a fluence of ~5e-7 erg/cm2 in the 15-150 keV band). The XRT then slewed to the source position. The average 2-10 keV spectrum can be fit with a power law (gamma ~ 2.6) with a column density (nH ~ 4e23) that is larger than the expected line-of-sight value and those from previous X-ray observations. More information can be found in Romano et al. ATel 4148 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#538 31 May 2012 |
Following the detection of renewed activity from IGR J19294+1816
Sidoli et al. 2012 ATel 4136 report the results of a Swift observations of this source.
The XRT spectrum is well described by an absorbed power law model, with Gamma~1.25 and NH~ 8E22 cm-2. The authors also mention that a 2 keV absorbed (NH~ 4E22 cm-2) black body provides a good fit. They report the detection of X-ray pulsations at P=12.457 at a fraction of ~ 60%. More details in Sidoli et al. 2012 ATel 4136 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#537 30 May 2012 |
Fiocchi et al. 2012 ATel 4135 report the detection of renewed activity from the HMXB IGR J19294+1816. The source was detected with INTEGRAL/IBIS on may 26 2012. The 18-60 keV spectrum is well fitted by a power law model with Gamma~3.6. This detection is consistent with the rise of a new outburst and compatible with the known orbital period of 117 days. More details in Fiocchi et al. 2012 ATel 4135 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#536 17 May 2012 |
Bassani et al. 2012 report on analyses of Swift and INTEGRAL observations of
IGR J12319-0749 leading to its identification as a blazar.
The Swift/XRT observations allow the authors to refine the X-ray position of this source to < RA=12h 31m 57.67s Dec= -07deg 47' 19.2" (+- 3.8"), a position that is compatible with the Rosat source 1RXS J123158.3-074705, the radio source NVSS J123157-074717 classified as a z=3.12 QSO. The authors present the spectral analyses of the individual spectra and a of the combined Swift+INTEGRAL averaged spectra. They favour a power law with an high energy cut-off as the best model (Gamma=1.24 and Ecut=24.5 keV although with large uncertainties). The authors discuss the nature of this source and conclude that it is a flat radio spectrum QSO, it shows properties of a broad line AGN. It is classified as an extreme blazar. More details in Bassani et al. 2012 arXiV 1205.3037 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#535 11 Mai 2012 |
In an ApJ paper to be published on June 1st, 2012, vol 751,
Chaty & Rahoui present new ESO/VLT VISIR mid-infrared (MIR)
spectroscopic observations, which unveiled the supergiant
HMXB IGR J16318-4848: a compact object orbiting a supergiant B[e] star.
First, emission line diagnostics allowed them to characterize the unusually intense absorption of this source, which is due to the presence of absorbing material (dust and cold gas) enshrouding the whole binary system. Second, by fitting broadband infrared SED (ESO NTT/SofI, VLT/VISIR and Spitzer data) - with a phenomenological model for sgB[e] stars, adapted from Herbig Ae/Be stars, they show that the supergiant star is surrounded by an irradiated rim heated to a temperature of 3800-5500 K, and then by a viscous disk of dust component at an inner temperature of 750 K, with the compact object orbiting inside this disk. Both new data and a novative method led to this discovery:
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#534 9 Mai 2012 |
Patruno et al. 2012
accepted in ApJ report on reanalysis of data of
the 11Hz pulsar IGR J17480-2446 located in Terzan 5.
They first carefully check that the NS is spinning up in this system by verifying that the previously reported long-term pulse frequency derivative is the spin derivative. After reaching the conclusion that the source indeed is spun up at 1.4e-12 Hz/s, the authors discuss the history of the evolution of this system, focusing on 3 distinct evolutionary epochs: a dipole dominated spin down one, a wind one, a the current roche lobe overflow epoch. They conclude that the source has not yet reached spin equilibrium, that is has been spun up in the current phase for a few 1e7 years, and that it is in a exceptionnaly early Roche lobe overflow phase. They further discuss the apparent discrepancy between the age of this system and that of the globular cluster. Much more details and all calculations can be found in Patruno et al. arXiV 1112.5315 Sturm et al. 2012, accepted in A&A report on multi-instrumental, multi-wavelengths analysis of IGR J05414-6858 in the LMC. Thanks to XMM-Newton they refine the X-ray position of the source to: RA=05h 41m 26.62s Dec=-69deg 01' 23.0" (+- 0.52" at 1-sig, ie about 0.9" at 90%). This is compatible with the position of OGLEIII LMC175.4.21714 previously suggested as the optical counterpart, and the Swift X-ray position. The authors detect a 48% pulsation at 0.2262 Hz (4.4208s) in the X-ray light curve, which is not seen in the INTEGRAL hard X-ray data. This indicates that the primary in J05414-6858 is a neutron star. They also report possible modulations at 19.9 days which they interpret as the orbital period of the system. The optical counterpart is confirmed as a B0-1 IIIe, further confirming the Be-HMXB nature of this system. More details in Sturm et al. 2012 arXiV 1202.4967 Finally Ricci et al. 2012 ATel 4102 report the discovery of a new source IGR J02341+0228 from INTEGRAL observation of the Galactic pole. The source was first detected with ISGRI at RA=38.5249 deg DEC=2.4646 deg with an uncertainty of 5 arcmin. A follow up observation with Swift allowed a refined X-ray position to be found : RA=02h 33m 49.11s Dec=+02 deg 29' 25.5" (+-2") which is compatible with the position of the quasar QSO B0231+022 The spectral analysis of the INTEGRAL and Swift spectra lead to compatible results. The source spectrum is power-law like with an upper limit on the absorption estimated to 05e22 cm-2, and a spectral index ~2.1 (Swift) and ~1.5 (INTEGRAL). These are compatible with the spectra of type 1 AGN. Further to that Massaro et al. 2012 ATel 4103 report the detection of an Infra red counterpart in the WISE catalogue at the position of IGR J02341+0228. WISE J023349.19+022925 has the following magnitudes m(3.4 micron) = 12.117, m(4.6 micron) = 11.030, m(12 micron) = 8.633, m(22 micron) = 6.451 and is classified as a blazar candidate by the authors due to its positional compatibility with the radio counterpart to the QSO B source. More details in Ricci et al. 2012 ATel 4102 and Massaro et al. ATel 4103 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#533 7 Mai 2012 |
Barret 2012 report the results of timing analysis of RXTE observations of the 11Hz LMXB IGR J17480-2446. He reports the discovery of HF QPOs at frequencies between ~803 and ~875Hz although he does not confirm the marginal detection previously reported from another study. He remarks that, as usually observed in Z sources, the QPO have low RMS amplitude and coherence. Using the highest frequency found and assuming that it is an orbital frequency at the inner disc radius, Barret can estimate a lower limit of 18.5 km for a neutron star of 1.4 Msun. More details in Barret 2012 arXiV 1205.0564 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#532 26 Apr. 2012 |
Bodaghee et al. 2012 accepted in ApJ
present results from XMM observations of five IGRs located in the
direction of the Scutum Arm. They provide refined X-ray positions
for all sources with a 90%-confidence uncertainty radius of 2.5 arcsec.
Thus, these coordinates represent the most accurate X-ray positions
available. For most of these sources, the spectrum and timing information
from the soft X-rays are discussed for the first time.
The main results are listed below. IGR J18457+0244: R.A. =18:45:40.30 Dec.=+02:42:11.2 large column density (~8e23 /cm2) and possibly a redshifted iron line possible QPO or long pulsation (~4 ks) classification uncertain: probable AGN (Sey-2), HMXB possible IGR J18462-0223: R.A. =18:46:12.68 Dec.=-02:22:29.3 large absorbing column (~3e23 /cm2) and detection of an iron line discovery of a spin period: Ps=997(1)s obscured pulsar in an SFXT IGR J18482+0049: R.A. =18:48:15.32 Dec.=+00:47:34.9 large absorbing column (~4e23 /cm2) new obscured HMXB candidate IGR J18532+0416: R.A. =18:53:15.83 Dec.=+04:17:48.5 possible redshifted iron line possible QPO or long pulsation (~1.4 ks) classification uncertain: AGN or HMXB possible IGR J18538-0102: R.A. =18:53:48.42 Dec.=-01:02:28.3 spectral parameters are consistent with previously-proposed AGN classification. With two additional obscured HMXBs in the Scutum Arm region, the authors have slightly reduced the asymmetry in the left-right distribution of obscured HMXBs in the Galaxy. For more information, please see Bodaghee et al. (2012) accepted in ApJ: arXiV 1204.3645 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#531 20 Apr. 2012 |
Wijnands et al. 2012 MNRAS 422, L91 (submitted version at
http://arxiv.org/abs/1202.0489) report the (re-)analysis of two
XMM-Newton observations of IGR J17091-3624 made during
quiescence.
Contrary to what previously claimed from these observations, the authors
clearly detect the source at 0.5-10 keV fluxes of respectively 9 and 12 e-14erg/cm2/s
in obs. 1 and 2.
During both observation they obtain a photon index of 1.6 (+-0.5) while fixing the
absorption.
Wijnands and collaborators discuss their findings and assuming that the relation
between the quiescent luminosity and the orbital period holds for this particular
source estimate an orbital period between >4 d (at 10 kpc) and as high as
tens of days in case of a larger distance. They then discuss this in comparison
to GRS 1915+105 to which J17091-3624 is similar and that is known to have a
large ~34d orbital period.
More details in Wijnands et al. 2012
arXiV 1202.0489
Bernardini et al. 2012 accepted in A&A report the characterization of IGR CVs
through XMM INTEGRAL and Swift observations.
All sources of their sample (among which IGR J08390-4833, J18308-1232, J18173-2509, J16500-3307
J17195-4100, and J15094-6649) are classified as Intermediate Polar.
The authors report detections of pulse periods, and the results of spectral analysis of all these data. All details can be found in Bernardini et al. 2012 arXiV 1204.3758 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#530 16 Apr. 2012 |
Tomsick et al. (2012),
accepted in ApJ report the results of Chandra and
Parkes radio observations of IGR J11014-6103.
The Chandra image confirms the complexity of the morphology of the source. The latter is composed of a point source at R.A. = 11h 01m 44.96s, Decl. =-61deg 01' 39".6 (+-0.64" at 90%). An extension pointing to the North East direction (towards the SNR MSH 11-61A) is also clear in the image. A ~4 arcmin long tail, perpendicular to the NE extension is also detected. Spectral analysis of the extended emission is presented, and the overall properties of the system are discussed. The results presented in Tomsick et al. are all consistent with the point source being a pulsar even though no pulsations have been detected in the radio observations. IGR J11014Ð6103 is a likely Pwin. In this scenario the NE extension is the result of a bow shock due to the motion of the pulsar through the ISM. An association with the SNR MSH 11-61A is suggested, and if true, would imply a large kick velocity of 2400-2900 km s-1 for the pulsar. More details (including a discussion on the X-ray tail and association to the pulsar/NE extension) can be found in Tomsick et al. 2012 arXiV 1204.2836 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#529 11 Apr. 2012 |
Molina et al. (2012), ATel 4025 report the results of Swift observations
of IGR J03564+6242 and the implications of their findings.
The XRT pointings show the presence of a single X-ray source within the 99% INTEGRAL error box. This source has the following refined X-ray position: RA=03h 55m 41.79s Dec= +62d 40m 57.60s (90% confidence +-5.4" ). The bright radio source 4C +62.08 (asymmetric double radio source) has a position compatible with the X-ray source. It has a steep spectrum and a 38 MHz flux of 1.9 Jy. The authors also report the presence of optical (USNO B-1.0) and infra red (2MASS) counterparts with the following magnitudes: R=18.23, B=19.65 and I=18.07,J=16.71 H=16.12 and K=15.28. The radio loudness of the source is estimated to R_L=3.5. All these lead Molina et al. to the conclusion that the source is extragalactic. More details in Molina et al. ATel 4025 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#528 30 Mar. 2012 |
In Bodaghee et al. (2012), we announce sub-arcsecond X-ray positions for IGR J16393-4643
and IGR J17091-3621 that we found using short (1 ks) observations with Chandra-HRC.
The X-ray coordinates (J2000.0) of the absorbed HMXB pulsar IGR J16393-4643 are: R.A. = 16h 39m 05.47s Dec. = -46deg 42' 13.0" (error radius of 0.6" at 90% confidence) This new position excludes the infrared counterpart candidate 2MASS J16390535-4642137 (whose spectral class has been the subject of debate) that we proposed in Bodaghee et al. (2006) which was based on an XMM-Newton observation. The refined Chandra error circle points instead to a new counterpart candidate that is possibly blended with the 2MASS star. This new candidate, which is hinted at in images from Spitzer-IRAC (5.8 microns), suggests a large distance to the X-ray source (> 12 kpc). The black hole candidate IGR J17091-3624 was observed during its 2011 outburst providing X-ray coordinates of: R.A. = 17h 09m 07.59s Dec. = -36deg 24' 25.4" (error radius of 0.6" at 90% confidence). This position is compatible with those of the previously-proposed optical/IR and radio counterparts, solidifying the source's status as a microquasar. Three targets, IGR J14043-6148, IGR J16358-4726, and IGR J17597-2201, were not detected, but we were able to establish 3σ upper limits of, respectively, 1.7, 1.8, and 1.5E-12 erg cm-2 s-1 on their observed X-ray fluxes (2-10 keV). The non-detection of IGR J14043-6148 indicates variability favoring an AGN rather than a SNR. The upper limit for IGR J17597-2201 sets the boundary on the quiescent flux from a probable LMXB that has been dormant since 2008. For more information, please see Bodaghee et al. (2012) accepted in ApJ: arXiV 1203.0557 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#527 28 Mar. 2012 |
The nearly-simultaneous broadband energy spectrum of the recently-discovered transient IGR J17177-3656 was used by Ma (2012) as an input to an accretion-jet model. The results indicate that the accretion is probably driven by luminous hot accretion flow (LHAF), and a distance of between 21 and 25 kpc is proposed assuming a 10-solar-mass black hole. The results lend credence to the view that the LHAF can explain the steep correlation between the radio and X-ray luminosity. More information can be found in Ma (2012) to appear in MNRAS Letters: arXiV 1203.6031 Analysis of archival data from the Vista Variables in the Via Lactae (VVV) survey by Rojas et al. (2012) has revealed 5 near-infrared counterpart candidates inside the Swift-XRT error circle of the new X-ray transient IGR J17494-3030 (see IGR Mail #524; ATel #3984). Additional observations are needed in order to determine which of these is the counterpart to IGR J17494-3030. For more, please see Rojas et al. (2012) in ATel #4006: ATel 4006 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#526 23 Mar. 2012 |
Bozzo et al. ATel 3989 report the results of a Swift
observation of the recently discovered IGR J17494-3030.
They detect a single X-ray source within the JEM-X error box at RA=17h 49m 23.78s Dec= -30° 29' 59.3" (+-2.2 arcsec). The XRT spectrum is well fitted by an absorbed power-law with N_H~2.1 E22 cm-2 Gamma~2.5. No pulsations are detected with a 99% upper limit of 25% between 0.001 and 0.2 Hz. This position is not consistent with the Chandra source previously mentioned. More details in Bozzo et al. ATel 3989 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#525 22 Mar. 2012 |
Paizis et al. ATel 3988 observed the field around IGR J18179-1621 with
Chandra.
This allowed them to refine the position of the X-ray counterpart to this
relatively new IGR to RA=18h 17m 52.19s DEC= -16deg 21' 31.7" (+-0.6" at 90%) which is compatible with the Swift position reported by Li et al. The 2MASS source previously suggested as an IR counterpart falls within the Chandra error box and is therefore confirmed as the likely IR counterpart to the IGR. More details in Paizis et al. 2012 ATel 3988 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#524 13 Mar. 2012 |
Boissay et al. 2012 ATel 3984 report the discovery of
a new source with INTEGRAL/IBIS. IGR J17494-3030 is
detected in both the 20-40 keV and 40-80 keV energy ranges
with ISGRI, and in the 3-10 keV and 10-25 keV ranges with JEM-X.
The source position is RA= 17h 49m 24s DEC=-30d 30' 00" (+- 1.3'), with an high energy spetrum fitted with a power law with Gamma~1.7. Further to that Jonker & Maccarone 2012, ATel 3986 report the results of Chandra observations of the same field. They mention the detection of a faint source at 2arcmin from the INTEGRAL position CXOGBS J174918.8-302821, which may be the quiescent counterpart to IGR J17494-3030. More details in Boissay et al. ATel 3984 (see also erratum at http://www.astronomerstelegram.org/?read=3985) and Jonker & Maccarone ATel 3986 Papitto et al. 2012, accepted in MNRAS report the results of analysis of all the RXTE, INTEGRAL and Swift observations of IGR J17480-2446 during its October-November 2010 outburst. THe measure of the pulse phase evolution leads to the conclusion that the NS average spin up rate was 1.48e-12Hz/s over this period. This is compatible with a spin up due disc accretion. A disc inner radius of 47-93 km is estimated at the peak luminosity. They also present spectral analysis of these data and show that the spectrum is due to thermal comptonisation of 1 keV photons probably emitted by the NS surface. The properties of the comptonising medium are seen to evolve along the outburst, from a kt~20 keV plasma to kt~3 keV with a much larger optical depth. In the mean time to pulse fraction decreases significantly which may be due to the fact that a part of the accreted matter is not channeled to the pole but accreted evenly by the NS. Much more details in Papitto et al. 2012 arXiV 1203.4096 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#523 13 Mar. 2012 |
Luna et al. 2012 ATel 3960 report the results of Swift
observations of the IGR J17197-3010's field.
Two sources are detected in this field. -The first lies at RA= 17h 19m 51.7s Dec = -30d 02' 0.6" (+-4.3") and is consistent with a symbiotic star, already previously suggested as the likely counterpart. Luna et al., however, remark that this source is at 9arcmin from the IBIS source; adding that this source has a low X-ray flux the authors refute its association to the IGR source. -The second source is found at RA=17h 19m 48.52s Dec=-30d 17' 25.87" (+-4.1") is located at 6.8' from the IBIS position. The spectrum is well described by an absorbed plasma with kT=2.9 keV and Nh=0.2e22 cm-2. The authors mention that the closest source listed in SIMBAD is actually IGR J17198-3020 at 3.1 arcmin. More details in Luna et al. 2012 ATel 3960 Finger et al. 2012 ATel 3961 report the detection of the 11.82s of IGR J18179-1621 with the Fermi/GBM. The pulsation was detected at 84.5896 mHz (84.5908 mHz) with an rms amplitude 5.9 mCrab (8.5 mCrab) in data of Feb. 20-23 (Feb. 24-27) 2012. More details in Finger et al. 2012 ATel 3961 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#522 09 Mar. 2012 |
Nucita et al. 2012 accepted in New Astr. report the results of
2 XMM-Slew observations of IGR J17361-4441 located in the
globular cluster NGC 6388.
The XMM spectra are well fitted with absorbed power law, with photon indices slightly higher than previously measured with Swift. They then discuss the type of this source. They refute the possibility of the IGR to be an intermediate mass BH (an IMBH was suggested to lie in this cluster). They also refute the HMXB nature for this source and rather favour an LMXB. More details in Nucita et al. 2012 arXiV 1203.0965 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#521 05 Mar. 2012 |
Smith et al. 2012 accepted in ApJ, report the results of analysis
of the RXTE/PCA Galactic bulge scans focusing on Fast X-ray transients,
of which 3 are IGRs (17391-3021, 17544-2619, and 16479-4514).
They first compare the behaviour of the SFXTs, SFXT candidates to that
of the persistent sg-HMXB 4U 1700-377.
The confirm the orbital period of J17544-2619, and although they do not reproduce the orbital period of J17391-2619 independently, their new data increase the significance of the original results. More details and the analysis and classification of other source in Smith et al. 2012 arXiV 1202.6434 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#520 02 Mar. 2012 |
Halpern 2012 ATel 3949 presents a first analysis of the XRT observations
and reports a first X-ray position (but see below) and the discovery of a strong
signal in the periodogram at 11.82s with a pulse fraction of 27%.
This is interpreted as the signature of a HMXB with a pulsar.
Later, Li et al. 2012 ATel 3950 report a finer analysis of the same data.
They first report a pile-up corrected X-ray position (that differs slightly from
that published earlier). The source lies at: RA = 18h 17m 52.20s Dec = -16d 21' 31.9" (+- 2.2 arcsec at 90%). The spectra of the 2 Swift observations are well fitted by absorbed power law with Nh1=11.0e22 cm-2 and Nh2=15.1e22 cm-2, Gamma1=0.4 and Gamma2=0.7. The source has in both observations 3-10 keV fluxes compatible with those obtained from the JEMX detection. A Ks=11.4 IR counterpart, 2MASS J18175218-1621316 (RA =274.467438 dec=-16.358791) is well within the X-ray error box. More details in Halpern 2012 ATel 3949 and Li et al. 2012 ATel 3950 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#519 01 Mar. 2012 |
Tuerler et al. 2012 ATel 3947 report the discovery of a new source
with INTEGRAL.
IGR J18179-1621 is detected both by the IBIS and JEM-X telescopes, and
the best X-ray position is RA=18h 17m 52s DEC=-16d 21 '25" (+- 1.5 arcmin) The combined JEM-X and IBIS/ISGRI spectrum can be well represented by a cut-off power-law (Gamma~-0.5, Ecut~4.9 keV) plus a broad Gaussian absorption line at ~20.8 keV. The 3-50 keV flux obtained is 1.0 e-9 erg/s/cm2 Interpreting the absorption line as a cyclotron scattering would indicate that the source is a high mass X-ray binary pulsar with a magnetic field in the emitting region of ~1.7e12 G More details in Tuerler et al. 2012 ATel 3947 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#518 29 Feb. 2012 |
Lutovinov et al. 2012 Astr. Letter report the results of their
optical observations of 6 hard X-ray sources of which 4 are
IGRs:
A comprehensive characterisation of these two new classes is presented in the paper. The authors, in particular, discussed the reasons making these two classes completely new compared to the known classes of 1915+105. More details in Pahari et al. 2012 arXiV 1202.5894 Capitanio et al. 2012, accepted in MNRAS, present the results of their analysis of the long term monitoring of the same source with Swift and INTEGRAL. The beginning of the outburst, up to the transition to the soft state is similar to the behaviour seen in other source (HID and rms-intensity diagram show similar pattern). After the source showed a behaviour more similar to that of GRS 1915+105. They perform spectral analysis of the data and, in particular, show, through a time resolved spectroscopic approach to the rho-type data, that the heartbeat pattern corresponds to rapid emptying and refiling of the inner region of an accretion disc. Capitanio et al. 2012 discuss their results and by comparing 17091-3624 to GRS 1915+105 they suggest, that, in addition to being at a large distance, the source may also have a large inclination, which would explain its faintness. More details in Capitanio et al. 2012 arXiV 1202.6186 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#517 17 Feb. 2012 |
Krimm et al. 2012 ATel 3933, report that the Swift/BAT
detected a source consistent with XMMSL1 J182155.0-134719/IGR J18219-1347.
The source was then also labeled Swift J1821.8-1348.
It was detected by the XRT during a follow up pointed observation
at a refined position: RA=18h 21m 54.86s Dec= -13deg 47' 26.5" (90% confidence of 1.7"), placing it right in the Galactic plane. The source spectrum is quite absorbed and therefore the statistics of the fit is not very good. The authors obtain Nh~4.4e22 cm-2 and Gamma~0.2 (with and error of +-0.6). An IR counterpart from the Spitzer catalogue is found in the XRT error box. G017.3244+00.1344 lies at RA=275.478202, dec=-13.790732, and has magnitudes of 12.93, 12,34 and 11.89 at, respectively, 3.6 microns, 4.5 microns and 5.8 microns. 2MASS 18215463-1347232 is 4.6" from the XRT position and is therefore dismissed as potential counterpart. More details are provided by Krimm et al. and their main conclusion is that the source is very likely a Galactic X-ray binary. See ATel 3933 Note that Chenevez et al. 2012 ATel 3930 report the detection of several transient in the Galactic Bulge region with INTEGRAL/JEM-X, of which H1743-322/IGR J17464-3213. All details in Chenevez et al. ATel 3930 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#516 15 Feb. 2012 |
Patruno et al. 2012 ATel 3924 report a possible identification
of the optical Counterpart of IGR J17480-2446 from HST archival
observations.
The authors clearly resolve a close-by red giant object and the optical counterpart to the previously suggested faint IR candidate counterpart. The latter is thus identified as one candidate optical counterpart of IGR J17480-2446. The magnitudes of this object are F606W = 22.46 and F814W=19.14. The object lies at R.A. = 17h 48m 04.86s DEC = -24deg 46' 49.24" (±0.3" at 90%) A finding chart of the region and the Color-Magnitude diagram of Terzan 5 can be found at this URL: http://www.astro.uva.nl/~apatruno/17480.html Much more details in Patruno et al. 2012 ATel 3924 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#515 9 Feb. 2012 |
Finger et al. 2012 ATel 3917 report the detection of the pulsed
flux from IGR J19294+1816 which indicates that the source is entering
into outburst.
IGR J19294+1816 was detected with Fermi/GBM at pulsed flux ~15 mCrab in the 12-50 keV range. The pulsation has a barycentric frequency of 80.2754 mHz More details in Finger et al. 2012 ATel 3917 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#514 8 Feb. 2012 |
Rebusco et al. 2012 (accepted?) in A&A report a quick estimate
of the BH mass in this source based on arguments related
to the frequencies of HFQPOs. Assuming that the latter are due to non-linear resonances of oscillating modes in the disc, that the frequency ratio of the 2 HFQPOs reported in this source are in the 5:2 ratio, and by comparing with the HFQPOs of GRS 1915+105, they estimate a mass of about 6 solar mass for the BH. More details in Rebusco et al. 2012 arXiV 1202.0483 Altamirano et al. 2012 ATel 3913 report that, although not detected by Swift/BAT, IGR J17091-3624 is still active. The authors have analysed several Swift/XRT observations (Jan 26th through Jan 31st) during which the source was clearly detected. The 0.5-10 keV source spectrum is well fitted with an absorbed (Nh~1.35) power law with an index ~2.6. No significant aperiodic variability is detected. The author conclude that IGR J17091-3624 is either in a "normal soft state'' or may be showing an other class of variability than those already reported. More details in Altamirano et al. 2012 ATel 3913 Further to this, Drave et al. 2012 ATel 3916 report that the same source was detected by INTEGRAL on Feb. 5, 2012 at a 18-40 keV (40-100 keV) flux of ~20 mCrab (20 mCrab). The source is also detected at a much lower flux in the 3-10 keV band by JEM-X and this may imply that IGR J17091-3624 may be undergoing a soft to hard spectral state transition. More details in Drave et al. 2012 ATel 3916 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#513 30 Jan. 2012 |
Riggio et al. 2012
ATel 3892 used an RXTE observation
of IGR J17480-2446 to refine the X-ray position of this
transient accreting pulsar.
During the observation the source was eclipsed by the moon, and
the authors used the ephemeris of the satellite to reconstruct the
precise position of the moon at the ingress and egress.
They derive a position for the X-ray source of: RA = 17h 48m 04.8245s DEC = -24deg 46' 48.88" with an estimated 1 sigma uncertainty of 0.04" This confirms the association with a chandra source previously suggested. More details in Riggio et al. ATel 3892 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#512 26 Jan. 2012 |
Sguera et al. 2012 ATel 3887 report the detection of the
symbiotic star IGR J12349-6434 (RT Cru) with INTEGRAL/IBIS
during Galactic plane scans performed between Jan 20 and 23 2012.
The source spectrum is power law like a photon index of ~2.4. A follow Swift observation allowed the authors to detect the source with the XRT instrument. The soft X-ray spectrum is well represented by an absorbed power law with Nh<1.78e22 cm-2 and Gamma~ -0.36. A hint of an iron emission line is also mentioned More details in Sguera et al. 2012 ATel 3887 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#511 12 Jan. 2012 |
Altamirano et al. 2012 accepted in ApJ report the discovery
of a high frequency QPO in the BHC IGR J17091-3624.
The feature has a frequency 64.8 Hz, thus very similar to the
67 HZ QPO of GRS 1915+105, to which the IGR is quite
comparable. A potential feature at 164 Hz is also reported strengthening the similarity to the 1915's HFQPOs. The implication of these findings are discussed in the view of the potential high distance, or low mass BH in the IGR source. More details in Altamirano et al. 2012 arXiV 1201.2106 King et al. 2012 accepted in ApJ, report observations of the same source performed with Chandra. They study the high resolution spectra of this source and mention the presence of absorption line that they attribute to a fast disk wind component in this system. Their simultaneous EVLA observation permits them to conclude that jet activity was quenched at the times of the Chandra observations. The presence of a disk wind when in soft state is compatible with what had been observed in other such sources More details in King et al. 2012 arXiV 1112.3648 Drave et al. 2012 accepted in A&A report the discovery of X-ray pulsations in RXTE observations of the region of the SFXT IGR J17544-2619. The pulsation is found at 71.49s. The authors discuss the association of this feature with all (known) potential sources present in the RXTE/PCA fov and favour IGR 17544-2619 as the origin of this pulsation. This, and the known orbital period of the source, place it within the Sg region of the Corbet diagram. More details in Drave et al. 2012 arXiV 1201.2284 Masetti et al. 2012 accepted in A&A report the results of Optical spectroscopy of 22 sources detected by INTEGRAL, 20 of which are IGRs. All results and discussion can be found in Masetti et al. 2012 arXiV 1201.1906 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#510 6 Dec. 2011 |
Lanzuisi et al. 2011 accepted in MNRAS report on analysis of
archival (INTEGRAL, Swift) and new (Suzaku, Fermi) data of
the blazar IGR J22517+2217.
They mention that the source underwent a strong flare in 2005 (INTEGRAL, Swift data) and is in quiescence since then (Suzaku, Fermi). They build the SED of these two different states and fit and interpret it within the leptonic one-zone synchrotron and inverse compton model. Both states show spectra dominated by the high energy hump that peaks at about 1e20-1e22 Hz that has a luminosity at least 2 order of magnitudes higher than the synchrotron peak (at ~1e11-1e14 Hz). The authors discuss the implication of their finding, and conclude in particular that the high energy hump is due to external inverse Compton while SSC component is negligible. The variability of the source is explained as due to variations of the total number of emitting electrons. More details in Lanzuisi et al. 2011 arXiV 1112.0472 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#509 29 Nov. 2011 |
Jain et al. 2011 ATel 3785 report the detection of sporadic intensity
modulation in the BAT 15-50 keV light curve of the SFXT IGR J16207-5129.
The modulation has a period of of 9.726 d that can be the orbital period of the X-ray binary. The authors further discuss their findings in lights of previous studies, and report that the prolonged reduction in the X-ray flux previously detected with Suzaku and interpreted as a possible eclipse does not in fact coincide with the phase at which the Swift-BAT light shows lowest intensity. In case where the found period is the orbital period the suzaku event would likely be an absorption event More details in Jain et al. 2011 ATel 3785 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#508 25 Nov. 2011 |
Potter et al., 2011 accepted in MNRAS report the results of their optical photo-polarimetric studies of 2 intermediate polars, one of which being IGR J15094-6649 (dubbed IGR J1509-6649 in their paper). The magnitudes observed in the I (14-15) and B (15-15.7) bands are consistent with that (previously reported ) of the V band. The authors report the discovery of circularly polarised light in both these bands. The polarised signals are spin modulated and show varying amplitudes (1-2.5%). A potential beat frequency is also seen which would imply an orbital period of 4.73 hr, that would present a 1d alias with the orbital period previously obtained from the Halpha studies of the source. The authors discuss the implications of their findings in terms of origin of the signal and geometry of the source. More details in Potter et al. 2011 arXiV 1111.5482 Krimm et al. 2011 ATel 3780 reports the detection of renewed activity of the SFXT IGR J18483-0311seen with Swift/BAT. The 15-50 keV flux has increased by a factor of ~15 between Nov 18 2011 and Nov 23 2011. All details in Krimm et al. 2011 ATel 3780 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#507 16 Nov. 2011 |
Altamirano et al., 2011 ApJ, 742, L17 report a detailed analysis of the 2011 RXTE observations of the BHC IGR J17091-3624. The authors identify 7 patterns of variability by inspecting the source's light curves. These are similar to classes seen in GRS 1915+105, although the typical timescales of the variability and the brightness are respectively shorter and fainter in IGR J17091-3624. By discussing the behaviour of IGR J17091-3624 in the context of models suggested for GRS 1915+105 the authors propose that either the models based on Eddington Luminosity fail for the IGR source, or that the latter source is at a distance well above 20 kpc, or that it harbours a very light black holes All details can be found in Altamirano et al. 2011 ADS link | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#506 14 Nov. 2011 |
Papitto et al. (2011), accepted in A&A, report the results of their observations
of the recently discovered source IGR J17498-2921.
They present analysis of observations made with both the RXTE and the Swift satellites. They detect a coherent pulsation at 400.99018734 Hz, and by analysis the modulations of this pulsation they can derive an orbital period of ~3.84 hr. They also estimate a mass of the donor between 0.17 Msun (lower limit) and 0.48 Msun (upper limit assuming it does not fill its Roche lobe). The authors also present the results of spectral analysis of RXTE and Swift data. The spectra are well modeled with absorbed power law with Gamma comprised between 1.7 and 2 except close to quiescence where it is much softer. More details in Papitto et al. arXiV 1111.1976 De Rosa et al. 2011 ,accepted in MNRAS, present an overall X-ray study of several (33) type 1.8-2 AGNs of which 15 are IGRs. The latter have been observed with dedicated XMM observations, and, for all of these sources, the results of simultaneous XMM+INTEGRAL spectral fits are presented. The authors also discuss the global properties of this sample of sources. More details in De Rosa et al. 2011 arXiV 1111.1946 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#505 25 Oct. 2011 |
Sidoli et al. (2011) report on a 40-ks XMM-Newton observation of the supergiant fast X-ray transient (SFXT) IGR J16418-4532 performed on Feb. 23, 2011. The source showed strong variability exceeding two orders of magnitudes, with several bright flares of different durations (from a few hundreds to a few thousands seconds) and sometimes with a quasi-periodic behavior. A pulse period of 1212+/-6 s was measured, confirming that this binary contains a slowly rotating neutron star. During the periods of low luminosity the source spectrum is softer and more absorbed than during the flares. A soft excess is present below 2 keV in the cumulative flares spectrum, possibly due to ionized wind material at a distance similar to the neutron star accretion radius. The kind of X-ray variability displayed by IGRJ16418-4532, its dynamic range and time scale, together with the sporadic presence of quasi-periodic flaring, are all suggestive of a transitional accretion regime between pure wind accretion and full Roche-lobe overflow. These authors discuss for the first time this hypothesis to explain the behavior of IGR J16418-4532 and, possibly, of other SFXTs with short orbital periods. Please see Sidoli et al. (2011) accepted in MNRAS: arXiV 1110.5218 (I warmly thank Lara Sidoli for writing the above portion of this IGR circular) Kaur et al. (2011) confirm the NIR counterpart to IGR J17407-2808 using a 270-s observation taken on Oct. 19, 2011, in the Ks band with the WIYN telescope. A faint (16.6+-0.3 mag) star is detected at a position that is consistent with the known Chandra and IR positions. This is an order of magnitude fainter than in earlier observation (from 2008) with the ESO, and with the Ks-band magnitude reported recently by Greiss et al. (2011). This variability of the NIR counterpart is further confirmation of its association with the IGR and CXOU sources. For more, please see Kaur et al.: ATel 3695 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#504 18 Oct. 2011 |
Romano et al. (2011) report that the SFXT candidate IGR J17407-2808 was detected
in outburst first by Swift-BAT (peak flux of 0.3(1) ph/cm2/s in 15-150 keV), then by
Swift-XRT which found a source position of R.A. (J2000) = 17h 40m 42.08s Dec. = -28d 07m 26.5s with an error radius of 2.4-arcsec, the XRT position is 1.6-arcsec away from (and consistent with) the position of the previously-proposed counterpart CXOU J174042.0-280724. The XRT-produced light curve and spectrum show, respectively, a peak of 10 cps with a dynamic range of 100 (i.e., several times brighter in soft X-rays than in previous observations), and nH ~ 1.5E22 /cm2 with gamma~0. The source was not detected with Swift-UVOT. For more information, please see Romano et al.: ATel 3685 Prompted by this outburst of IGR J17407-2808, Greiss et al. (2011) examined recent near-infrared VVV Survey observations of the field taken while the source was in quiescence. A potential infrared counterpart is detected at R.A. (J2000) = 17h 40m 42.01s Dec. = -28d 07m 25.0s (uncertainty ~ 0.1 arcsec). This is 0.67 arcsec from (and consistent with) the proposed soft X-ray counterpart CXOU J174042.0-280724. This infrared counterpart has magnitudes (corrected for reddening) of J = 15.1, H = 15.0, and Ks = 14.9. The same star is found with CTIO at a dereddened r-band magnitude of 16.2. These values suggest a late F-type dwarf at a distance of ~4 kpc, which rules out a supergiant companion. Therefore, IGR J17407-2808 is not a SFXT candidate, but is likely to be a LMXB. Further discussions can be found in Greiss et al. : ATel 3688 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#503 29 Sept. 2011 |
Bozzo et al. 2011, accepted in A&A report the results of a multi-instrumental
campaign on the recently discovered source IGRJ17361-4441.
They report the spectral parameters obtained from the fits to the 0.5-100 keV spectrum (Swift/INTEGRAL), while they do not detect any specific timing feature from the RXTE data. The best fit model is an absorbed black body plus a cut off power law (Nh=0.8e22 cm-2, Gamma=1.0, Ecut=24 keV, kTbb=0.08 keV) The source is also not detected by the ATCA at radio wavelengths. The authors interpret their data and results, and conclude that a black hole primary for this object is not likely, and that the source is a low mass X-ray binary. More details in Bozzo et al. 2011 arXiV 1109.5719 Romano et al. 2011 accepted in MNRAS report the results of Swift monitoring of IGR J16418-4532, a candidate SFXT. The authors first provide a refined position of this source (RA=17h 41m 50.65s, dec=-45 deg 32' 27.3" with an error of 1.9") and further confirm its association to the previously proposed IR counterpart. Through the analysis of the source's eclipse they confirm the supergiant nature of the companion. They, then, interpret their data within the context of the accretion of spherically symmetric clumpy wind, and obtain masses for the clumps from 5e16 to 1e21 g. The authors conclude that the X-ray bahaviour of the source suggests that it is an intermediate SFXT. More details in Romano et al. 2011 arXiV 1109.6165 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#502 27 Sept. 2011 |
Linares et al. 2011,
ATel 3661 report some results
of a Swift monitoring of the accreting ms pulsar
IGR J17498-2921:
In this paper, we present the first direct measurement of the spatial cross-correlation function between 79 hard X-ray detected HMXBs (many of which are IGRs) and 458 active OB star forming complexes in the Milky Way. Clustering between the two populations is detected with a significance above 7-sigmas for distances < 1 kpc. The average offset of 0.4+-0.2 kpc between HMXBs and OB associations is consistent with a displacement which is due to natal kicks at velocities of the order of 100+-50 km/s. The characteristic scale of the correlation function suggests an average kinematical age (since the supernova phase) of ~4 Myr for the HMXB population. Despite being derived from a global view of our Galaxy, these signatures of HMXB evolution are consistent with theoretical expectations as well as observations of individual objects. More information, including a comprehensive list of the most recent HMXB distances and classifications, can be found in Bodaghee et al. (2011) arXiV 1109.3466 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#501 15 Sept. 2011 |
Chenevez et al. 2011,
ATel 3646 report on INTEGRAL results
on the field around the Galactic centre.
They mention a marginal detection of the X-ray Burster IGR J17498-2921
with JEM-X in its lowest energy range, while the source is not
detected above 10 keV with neither JEM-X nor ISGRI.
The authors conclude that the source is returning to quiescence More details in Chenevez et al. 2011 ATel 3646 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#500 13 Sept. 2011 |
Chakraborty et al. 2011, ATel 3643,
Chakraborty et al. 2011 ATel 3643 report the detection and analysis
of 10 thermonuclear X-ray bursts from IGR J17498-2921, one of which
showing a clear photospheric radius expansion, with a bolometric
max flux of 4.8e-8 ergs/cm2/s.
The authors can they estimate a distance similar to that previously suggested (7.6 kpc).
The authors further confirm the presence of burst oscillations in this source by detecting (at the 7 sigma level) burst oscillation in the tail of the PRE burst. More details in Chakraborty et al. 2011 ATel 3643 Curran et al. 2011, (A&A accepted) report on observations of 3 INTEGRAL associated PWNe, 2 of which being IGRs: No nIR/optical counterpart to the radio pulsar at the centre of IGR J14003-6326 is detected down to limiting magnitudes of Ks>17.2, H>18.0, J>19.2, i>21.2, R>21.0, V>21.8, B>22.3. Though a Ks=16.7 source is detected at ~2.6 sigma from the X-ray point source of HESS J1632-478 (source initially associated with IGR J16320-4751 though this was subsequently rejected), the probability of a chance superposition is >~70% so the source is likely unrelated. The authors confirm the magnitude of the previously suggested (Ks=16.4) counterpart to IGR J18490-0000 and approximate the probability of a chance superposition in the field to be 5%. They point out that if this is confirmed as the actual counterpart, it would be significantly brighter (>~2) than any other isolated pulsar, bar the Crab pulsar. This source is in fact, significantly brighter than the extrapolation of the X-ray spectra to that wavelength (Ks~23) hence an an unrelated foreground star is not totally rejected despite the low probability of chance superposition. More details in Curran et al. 2011 arXiV 1109.2451 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#499 09 Sept. 2011 |
Torres et al. 2011, ATel 3638,
report the results of NIR and
Chandra observations of the accreting ms pulsar IGR J17498-2921.
The suggested IR counterpart has a mean H mag = 16.0 with no brightening detected. This value is compatible with the pre outburst value of this source which indicates that this IR source is not related to the X-ray source. The Chandra spectra were fitted with an absorbed powerlaw with Gamma=1.75 and Nh=2.87e22 cm-2. The authors further discuss these findings and provide estimate of the quiescent magnitudes of the (true) IR counterpart More details in Torres et al. 2011 ATel 3638 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#498 08 Sept. 2011 |
Chen et al. 2011, accepted in A&A report the
results of Swift RXTE and INTEGRAL observations of
IGR J17473-2721 over its 2008 outburst.
They study the relation between the duration of the types I X-ray bursts and the source flux, and confirm the correlation between these two quantities seen in other such sources. They, however, find that the slope of the correlation differs between the increasing and decaying part of the outburst. They focus on the initial part of the outburst and remark that the cut-off energy of the X-ray spectra decreases while going from quiescence to and through the hard state. This is interpreted as a cooling of the coronal electrons by soft photons coming either from the disc or the NS surface. While analysing the behaviour of the burst (especially the fact that their spectra is entirely black body like) the authors conclude that the corona sits on top of the disc rather than on the NS surface More details in Chen et al. 2011 arXiV 1109.0788 van den Berg et al. 2011 ATel 3634 report the results of pre outburst optical and NIR observations of the field of IGR J17498-2921. < An optical source is found at RA=17h 49m 55.34s, Dec=-29d 19m 19.7s. Which is consistent with the Chandra position. The authors also conclude that this source is the same as the one previously reported from the Faulkes telescope. The source has R=23.2, I=21.06, and Halpha-R=0.4. The authors convert this to i' mag and since their value is compatible with the outburst one they conclude that the proposed counterpart is a probably a chance alignment. More details in van der Berg et al. 2011 ATel 3634 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#497 08 Sept. 2011 |
Pooley et al. 2011, ATel 3627 report the results of a Chandra observation
of IGR J17361-4441.
The transient is detected at RA = 17h36m17.418s, Dec = -44:44:05.98 with an error circle of 0.04" (statistical) estimated from the wavedetect tool. The authors also mention the presence of 4 additional sources whose positions match that of sources detected in a previous and deeper Chandra observation of this field. IGR J17361-4441 is located 2.7" away from the centre of the globular cluster, and the authors, therefore, dismiss an association with the IMBH. The source is not associated to any other sources from the globular cluster previously found, and Pooley estimate a quiescent luminosity of IGR J17361-4441 of 1e31 erg/s. More details in Pooley et al. 2011 ATel 3627 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#496 02 Sept. 2011 |
Russell et al. 2011,
ATel 3622 report the detection of an optical
star at a position consistent with that of IGR J17498-2921 with a significance
of ~4 sigma.
The source, detected in their Faulkes telescope observations, also has a position consistent with previously proposed near-infrared quiescent counterpart. The position derived by Russel and collaborators is RA= 17h 49m 55.4s, Dec = -29d 19' 19.6" (+/- ~0.3") They suggest that the source is likely to be to optical counterpart to IGR J17498-2921, and derive a magnitude of i' ~22.5. More details in Russell et al. 2011 ATel 3617 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#495 01 Sept. 2011 |
Ferrigno et al. 2011,
ATel 3617 report the results of radio observations
of the field around IGR J17361-4441 performed with ATCA.
No hint of radio emission was found within 4 arcmin from the Swift position of the source with RMS noise levels of 14.1 muJy, 19.0 muJy, 20.0 muJy, and 21.2 muJy at respectively 5.5, 9, 17, and 19 GHz. The authors further discuss the type of the source, and based on the radio-X-ray fundamental plane, dismiss an association with the IMBH at the centre of the globular cluster. A black hole nature for this source is, furthermore, not favoured. Based on these observations the authors also refine the upper limit on the mass of this central IMBH to 600 Msun. More details in Ferrigno et al. 2011 ATel 3617 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#494 30 August 2011 |
Chakrabarty et al. 2011,
ATel 3606 report the results of a Chandra
observation of the AMP IGR J17498-2921.
The source is detected with the HRC at RA = 17h 49m 55.35s Dec = -29d 19' 19.6" (with a 90% error radius of 0.6 arcsec) This is compatible with the published positions of the Swift X-ray, Chandra quiescent and IR counterparts. The authors also report that the ~401 Hz pulsations were detected at a 99.1 % confidence level with an amplitude of 11%. More details in Chakrabarty et al. 2011 ATel 3606 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#493 29 August 2011 |
Markwardt and Strohmayer 2011,
ATel 3601, report a refined
orbital solution for the AMS IGR J17498-2921.
Using all RXTE observations made 2011-08-13 and 2011-08-23 they find a coherent pulsation at 400.990187287 Hz (non corrected for the RXTE orbit and without clock correction applied), an orbital period 13865.615 s and a projected semi major axis 0.365108 lt-sec. They derive a range of masses between 0.17 and 0.22 Solar masses for the companion depending of the NS mass. More details in Markwardt and Strohmayer ATel 3601 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#492 26 August 2011 |
Wijnands et al. 2011, ATel 3595 report that the flux of IGR J17361-4441 measured over the past 9 days with Swift XRT is roughly constant at about 6-9e35 erg/s/cm2 (assuming d=11.5 kpc), which makes the source a very faint X-ray transient. The authors further discuss the type of the object and in particular mention that the very hard spectrum (photon index 0.6-1.0) is atypical for a neutron star LMXB, although some such systems have been seen with similarly hard spectra. Other types of system are also discuss and Wijnands et al. also mention the possibility of IGR J17361-4441 being an intermediate mass black hole. More details in Wijnands et al. 2011 ATel 3595 Mangano et al. 2011 ATel 3586 report that a new outburst of the SFXT IGR J08408-4503 was seen with Swift/BAT. They report the analysis subsequent XRT observations of this event. All details in Mangano et al. 2011 ATel 3586 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#491 24 August 2011 |
Cavechhi et al. 2011, accepted in ApJL report the results of
the analysis of all RXTE observations of the 2010 outburst
of IGR J17480-2446.
They study the properties of the bursts from this source. They have a typical duration of 100-200 s. The authors mentioned that when the persistent luminosity is <15% Ledd the bursts can be classified as type I, while at L=15-35% Ledd they cannot classify them due to the lack of evidence for cooling. Cavecchi and collaborators report that burst oscillations were detected in all bursts and they discuss the implications of their findings within the framework of theoretical models for burst oscillations. The main conclusion is that, in this source, burst oscillations are probably due to magnetic confinement of the burning material. More details in Cavecchi et al. 2011 arXiV 1102.1548 Kennea 2001 ATel 3578 report a re-examination of recent and archival Swift observations of the region of the recently reported new SMC transient. He finds that the position of 2009 Swift counterpart to IGR J00515-7328 lies 1.9" away from the position of the new transient, therefore the positions of the two objects are compatible (within the uncertainties). He also compares the fluxes and spectral shapes between the two sources, and finally comes to the conclusion that the new transient is very likely IGR J00515-7328. More details in Kennea 2011 ATel 3578 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#490 22 August 2011 |
Linares et al. 2011, ATel 3568
report the detection of a
type I X-ray burst with burst oscillation during an RXTE
observation of IGR J17498-2921, with a total duration (PCA
bandpass) of 30s.
The X-ray spectrum is well described throughout the burst by an absorbed blackbody model with a cooling tail typical of thermonuclear (type I) X-ray bursts. IGR J17498-2921 is thus confirmed to be a burster, and is the 7th out of the 14 currently known AMPs to show thermonuclear bursts. Evidence for a moderate photospheric radius expansion is found in both the rise and decay. Using the maximum inferred luminosity the authors estimate a distance to the source of ~7.6 kpc. They also report the presence of a 401 Hz frequency during 2-3 second interval in the tail of the PRE episode. More details in Linares et al. 2011 ATel 3568 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#489 17 August 2011 |
Markwardt et al. 2011, ATel 3561 and Papitto et al. 2011 ATel 3563
both worked on trying to find an orbital solution of the source based
on the RXTE data.
The former team found two candidates orbital solutions at 3.8432 hr and 4.0834 hr,
while the second using more RXTE data conclude that the orbital solution
is 3.84281hr.
More details in Markwardt et al. 2011
ATel 3561
and
Papitto et al. 2011
ATel 3563
Greiss et al. 2011, ATel 3562 report the results of their search for
an IR counterpart to this source.
They report the presence of a NIR source at RA = 17h 49m 55.33s Dec = -29o 19' 19.6" (RMS of 0.1 arcsec) with J = 17.45, H = 15.73 and Ks = 15.10. They also obtain an extinction lower than that obtain from the fit to the X-ray spectra. The de-reddened magnitudes are consistent with a late K or early M type star, which would indicate the source is an LMXB. The authors further discuss on the distance and association to the X-ray source. More details in Greiss et al. 2011 ATel 3562 Gibaud et al. 2011, ATel 3565 report the discovery of a new hard X-ray source IGR J17361-4441 with INTEGRAL/IBIS. The best determined source position is RA=264.046 (17h 36m 11.04s) DEC=-44.689 (-44deg 41' 20.4") (+- 3 arcmin). The globular cluster NGC 6388 is within the IBIS error box. The IBIS/ISGRI spectrumcan be well described bya power-law with photon index Gamma=2.6 Ferrigno et al. 2011 ATel 3566 report the results of a Swift follow up observation of this field. The source position is refined to RA= 17h 36m 17.5s Dec=-44deg 44' 07.1" (+- 2.1 arcsec). These locate IGR J17361-4441 within the Globular Cluster NGC 6388. The X-ray spectrum is well represented by an absorbed power-law with Gamma~0.7 and NH<2.6 E21 cm-2. More details in Gibaud et al. 2011 ATel 3565 and Ferrigno et al. 2011 ATel 3566 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#488 16 August 2011 |
Ferrigno et al. 2011,
ATel 3560 report the detection
of one type I X-ray burst from IGR J17498-2921
in the INTEGRAL JEM-X light curve.
The burst properties are the following duration of the event 15 s decay time ~6 s Burst spectrum -> Black body with kT~1.4 and radius 19 km (at 10 kpc) More details in Ferrigno et al. 2011 ATel 3560 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#487 15 August 2011 |
Bozzo et al. 2011,
ATel 3555 report the results of a Swift
follow up observation of IGR J17498-2921.
A single X-ray source is detected by the XRT within the IBIS
error box at: RA = 267.4819 (17h 49m 55.7s) Dec = -29.3227 (-29deg 19' 21.7") with an estimated uncertainty of 7 arcsec due to a strong pile up. The pile-up corrected XRT spectrum is well represented by a simple absorbed power-law model with Nh~3.0E22 cm-2 and Gamma~1.9 A further re-analysis of this data and of an additional Swift pointing permitted Bozzo et al. 2011 ATel 3558 to refine the position to RA =17h 49m 55.33s Dec = -29deg 19' 20.6" with an uncertainty of 1.9" (90% conf. level) An increase of the X-ray flux is also reported. More details in Bozzo et al. 2011 ATel 3555 and ATel 3555 Papitto et al. 2011 ATel 3556 report the results of an RXTE observation of the same source. They mention the presence of signal at ~401 Hz in the power density spectra which may suggest the source is an accreting ms pulsar. More details in Papitto et al. 2011 ATel 3556 Jonker et al. 2011 ATel 3559, report the analysis of archival Chandra data of the same field. They detect a faint source consistent with being the quiescent counterpart to IGR J17498-2921 at R.A.(J2000)=17h 49m 55.38s Dec (J2000)=-29o 19' 19.7" with a typical 0.6" uncertainty. They estimate a quiescent flux of ~2.5e14 erg/cm2/s More details in Jonker et al. 2011 ATel 3559 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#486 13 August 2011 |
Gibaud et al. 2011,
ATel 3551 report the discovery of
a new source IGRJ17498-2921 with INTEGRAL/IBIS.
They determine the following position for this source RA=17h 49m 49s DEC=-29deg 21' 14" with a 90% error radius of 2.3 arcmin. The IBIS/ISGRI spectrum can be well described by a a power-law with a photon index 1.9 and an estimated 20-100 keV flux from the spectral fit is ~3.4e-10 erg/s/cm2. More details in Gibaud et al. 2011 ATel 3551 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#485 9 August 2011 |
Sturm et al. 2011, ATel 3537 report that the LMC Be X-ray binary IGR J05414-6858 was detected to be in a X-ray outburst with Swift. The X-ray spectra were fitted with a model consisting of an absorbed power-law with a photon index 0.83. The previous outburst in 2010 had been classified as a type II and it is for the moment not possible to tell if the current one is of the same type More details in Sturm et al. 2011 ATel 3537 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#484 4 August 2011 |
Rodriguez et al. 2011, accepted in A&A report on the first four simultaneous
multi-wavelength observations of the BHC IGR J17091-3624 performed
during february-march 2011.
We analysed radio (ATCA) and X-ray (Swift, INTEGRAL, RXTE) data and first conclude that the source was in a hard state in the first 2 observations and that it transited to a soft intermediate state later. Using the luminosity at the state transition we estimate a distance to the source of ~11 to ~17 kpc, for a typical BH mass of 10 Msun. The radio vs X-ray luminosity properties of this source are similar to those of other black hole binaries only if IGR J17091-3624 lies at a distance greater than 11 kpc, with a preferred distance of 17 kpc. The source radio-X-ray behaviour observed during these observations is more typical to that of "standard" BH binaries (GX 339-4 or H1743-322) than that of GRS 1915+105. More details in Rodriguez et al. 2011 arXiV 1108.0666 Ricci et al. 2011, A&A, 532, A102 present an analysis of the hard X-ray spectra of 165 Sey-AGN with INTEGRAL, a large number of which are IGRs. Main spectral differences and typical properties of the different type of AGN are presented and discussed. More details in Ricci et al. 2011 arXiV version | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#483 2 August 2011 |
On a recently published paper, D'Ai et al. 2011, A&A, 532, A73
report the results of Swift and Suzaku observations of the HMXB IGR J16493-4348.
They extracted an average Swift/BAT spectrum over 54 months of observations of the source, which they fitted together with Swift/XRT and Suzaku pointed observations. Several phenomenological models are used to fit the spectrum. In all spectral fits, the authors report the presence of a large absorption feature of ~10 keV width at ~30-33 keV which they interpret as a resonant cyclotron absorption feature. Based on this finding they estimate a surface magnetic field of ~ 3.7 e12 G. Much more details in D'Ai et al. 2011 A&A, 532, A73 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#482 28 July 2011 |
Pavan et al. 2011 accepted in A&A
report their results of multi-instrumental observations
of IGR J11014-6103.
L. Pavan reports: Archival XMM data showed that the source, at X-ray wavelengths, is comprised by three different emitting regions: a 4-arcmin extended cometary-like tail (detected also in Swift, ASCA and Einstein data), and two sources separated by ~22 arcsec, both located at an end of the cometary-like tail. One of these sources is extended (8.1 arcsec). A search for optical and NIR counterparts did not lead to any detection inside the 90% XMM error circle. At radio waveband instead (MGPS-2, 843 MHz) we found a possible counterpart, laying close to the 8.1arcsec extended source. All the three components could be well fit by using a power-law model. The joint XMM-INTEGRAL spectrum, also fit with a simple absorbed power-law model, provided a Photon Index 1.6+/-0.15. Based on our spectral and timing analysis, we suggested that IGR J11014-6103 might be a pulsar wind nebula produced by a high-velocity pulsar. Comparison with similar sources like PSR B2224+65 and PSR J0357+3205 are also discussed in the paper. As for the interpretation of the joint XMM+INTEGRAL emission, we found a similar emission in the case, e.g., of the young pulsar( and PWN) AX J1838-0655. All details in Pavan et al. 2011 arXiV 1107.2045 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#481 27 July 2011 |
Chakraborty et al. 2011 accepted in MNRAS report the results
of RXTE spectral analysis of IGR J17480-2446.
They find a large hysteresis in the C-like HID during the Atoll state.
By comparison with other sources they also mention that the nature of spectral evolution during the outburst does not depend on the peak luminosity. The spectra of the source show the presence of two components (and an iron line in emission not discussed): a black body and a power law tail. The analysis of the variations of these component makes the authors conclude that they are probably connected and that they are somehow linked to cause the spectral evolution. They compare the source behaviour to other similar sources and conclude that it could be an analogue to the clock burster GS 1826-238 More details in Chakraborty et al. 2011 arXiV 1102.1033 Mason et al. 2011 accepted in A&A report on NIR observations of the HMXB IGR J18027-2016. Their analysis permits to refine the spectral type of the companion to B0-1 I, with ranges of masses comprised in the 18.6+/-0.8 -- 21.8 +/- 2.4 Msun depending on the assumptions used. They also provide estimates for the mass of the neutron star of 1.4 +/-2 -- 1.6 +/- 0.3 Msun. More details in Mason et al. 2011 arXiV 1106.2045 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#480 4 July 2011 |
In two recently accepted papers Curran et al. 2011 accepted in MNRAS and A&A report the results of their infrared observations of several sources including 3 IGRs. In the first paper (arXiV 1107.1392, to be published in MNRAS) the nature of the counterpart to CXOU J174437.3-323233 one of the X-ray counterpart to IGR J17448-3232 is discussed. An infra red counterpart to the source is discovered. The authors also present its SED which is consistent with a single power law over 5 order of magnitudes in frequency. The authors dismiss an association of this source with the extended source also suggested as an X-ray counterpart to the IGR and suggest that this object is a blazar seen through the Galactic plane In the second paper (arXiV 1107.2045, to be published in A&A) the IR counterparts of two LMXBs IGR J17379-3747, and J17585-3057 are clearly identified and the position of both sources are given. In the case of the former the authors also provide the optical magnitudes of the source, present its SED, which is consistent with a stellar-like black body emission. The latter is also present in the GLIMPSE catalog and the Spitzer magnitudes are also reported. The authors mention that the extrapolation of the SED from the Spitzer data overestimates the Ks magnitudes which either indicates an excess in the Spitzer band or that the source is variable. More details in Curran et al. arXiV 1107.1392 and arXiV 1107.2045 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#479 4 July 2011 |
Paizis et al. 2011
accepted in ApJ, present the results of
multiwavelength follow up observation of IGR J17177-3656.
This object was discovered on 2011 March, 15th with INTEGRAL and Paizis and collaborators obtained (quasi) simultaneous Chandra-INTEGRAL, Swift, NIR and Radio observations. They study and present the properties of the source and its putative counterparts at all wavelengths. With all the information at hand, the authors propose that IGR J17177-3656 is an LMXB, seen at high inclination, probably hosting a black hole. More details in Paizis et al 2011 arXiV 1107.0201 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#478 30 June 2011 |
Bozzo et al. 2011
accepted in A&A report the results of a long XMM-Newton
observation of the SFXT IGR J18410-0535, as well as re-analysis of previous
Swift and ASCA data.
A bright flare is observed during the observation. A full time-resolved spectral analysis of the observation is performed and reported, which leads them to conclude that the X-ray flare is probably due to the accretion of a massive clump by the neutron star. They estimate a mass and radius of 1.4e22g and 8e11cm for this clump. The temporal analysis of the XMM data do not reveal the presence of the previously reported ~4.7s pulsation. By re-analysing archival ASCA and Swift data Bozzo and collaborators conclude that the pulsation was in fact an artifact due in one case to statistical fluctuations and instrumental effects in the other case. Much more details in Bozzo et al. arXiV 1106.5125 Note that Mangano et al. 2011 ATel 3453 report the detection of a fast outburst from this object on 2011 June 24 seen and followed with Swift. All the details can be found at ATel 3453 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#477 23 June 2011 |
Sguera et al. 2011
accepted in MNRAS present the results
of a long term INTEGRAL monitoring of IGR J17354-3255
and results from Swift observations of this source.
This object is a weak and persistent source that occasionally show X-ray flares. Based on Swift observations the authors show that the ratio between the maximum flux (of the flares) and the minimum (non-detection) is at least 300. With the INTEGRAL data they confirm the 8.4 day period, interpreted as an orbital period. The spectral and temporal analysis are indicative of a supergiant X-ray binary, although the ratio of flux variation is more compatible with an intermediate SFXT. The authors also discuss the possibility of the association of the IGR with an Agile MeV source. More details in Sguera et al. arXiV 1123.4209 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#476 16 June 2011 |
Panessa et al. 2011 accepted in MNRAS report the result
of a study of a sample of 14 Narrow Line Sey 1 observed with
INTEGRAL. This sample includes at least five sources discovered by INTEGRAL (hence IGRs). For each source XMM, Swift and INTEGRAL data are examined, and the main properties are reported. All the details in Pannessa et al. arXiV 1106.3023 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#475 10 June 2011 |
Pahari et al. 2011 ATel 3418 report some results of recent
RXTE observation of the BHC IGR J17091-3624.
This source has been observed to show X-ray variability similar to that seen in GRS 1915+105. It, in particular, was found in classes similar to the rho and beta types of the latter. In the most recent observations, Pahari remarked that IGR J17091-3624 only showed the rho type (also dubbed heartbeat oscillations). The peculiarity is that both small and large amplitude oscillations are seen in the IGR source, with intervals of large bursts and short bursts appearing alternatively. The characteristic time scale is ~40.25 sec. The peak-to-dip count rate ratio is ~3-5 for large bursts and 1.5-2 for short bursts. From 26 May 2011 to 03 June 2011 the number of large burst intervals and their maximum peaks are seen to decrease, and they disappeared on 04 Jun 2011. Much more details, including a description of the mHz QPOs associated to the recurring burst can be found in Pahari et al. 2011 ATel 3418 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#474 01 June 2011 |
Malizia et al. 2011 ATel 3391 report the results of Swift follow-up
observations of 2 IGRs
IGR J17472-7319 1 source is detected within the IBIS error box at : R.A.= 17h 43m 11.1s Dec.= -73d 19m 22.6s (+/-5.0 arcsec). The source has however a rather low significance, and may be slightly extended. No counterpart is found for this object at other wavelengths. The Swift-XRT data are well fitted with a simple power law with Gamma~2. IGR J23558-1047 2 sources are detected by the XRT one within the IBIS 90% error box, and one within the 99% positional uncertainty of IBIS.
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#473 30 May 2011 |
Krivonos et al. 2011
ATel 3382 report the discovery and identification
of two new IGRs.
IGR J04221+4856: INTEGRAL detects a bright source at RA=65.53, Dec=48.95 (+-4 arcmin), probably associated with the bright ROSAT source 1RXS J042201.0+485610. This Rosat source was suggested to be a Seyfert 1 AGN at z=0.114 IGR J19491-1035: was first detected with IBIS in the 17-60 keV range. Follow-up Swift/XRT observations shows the presence of a single source in the field at RA=19h49m08.69s, Dec=-10h34m34.46s (+-4 arcsec). This is spatially consistent with the galaxy 2MASX J19490928-1034253 whose optical spectrum can be found in the 6dF Galaxy Survey, and that shows series of broad Balmer emission lines and OIII 4959,5007 narrow emission lines at z=0.02402. The IGR is therefore identified as a Seyfert 1 AGN. More details in Krivonos et al. ATel 3382 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#472 19 May 2011 |
Bozzo et al. 2011 accepted in A&A report the results of
INTEGRAL and Swift observations of IGR J19294+1816
during its last (2010) outburst.
The authors report that the source flux decayed smoothly over a period of 2 months without showing dramatic spectral changes. They detect pulsations at 12.5s up to an energy of 50 keV and report a marginal detection of the ~116d period. Bozzo et al. discuss their results and conclude that IGR J19294+1816 is very probably a Be-HMXB rather than an SFXT More details in Bozzo et al. arXiV 1105.2727 Maiorano et al. 2011 accepted in MNRAS report on a new method its results to identify AGN amongst unidentified IGRs. The authors first describe the method which relies on the cross calibration of Radio, IR and the IBIS catalogue, and for 4 sources subsequent X-ray (Swift) observations. They discuss the case of 8 objects. 3 objects are AGNs, 3 more are AGN candidates, one is a possible starburst although they do not exclude chance association, and for an 8th one the lack of data do not permit them to conclude on the nature. More details in Maiorano et al. arXiV 1105.3089 Bazzano et al. 2011 ATel 3361 report the discovery of two new sources in the last INTEGRAL Galactic Plane monitoring. These are IGR J19203+1328 R.A.= 290.145 deg Dec= 13.47 deg and IGR J19094+0415 RA=287.414 deg Dec= 4.254 deg both having a positional uncertainty of 3 arcminutes. These sources are detected at 18-40 keV flux of, respectively, 16.5 mCrab and 18.9 mCrab. None is detected above 40 keV. More details in Bazzano et al. ATel 3361 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#471 13 May 2011 |
Tomsick et al. 2011 ATel 3342 report on the results of their
Chandra observation and subsequent IR counterpart identification
of IGR J16413-4046
CXOU J164119.4-404737 lies at a position consistent with the previously proposed Swift counterpart at: R.A. = 16h 41m 19s.49 Decl. = -40d 47' 37".8 (+/- 0".64). This is consistent with the position of 2MASS J16411948-4047378 (H = 15.08, Ks = 13.97) that is not present in the DENIS near-IR/optical or USNO optical catalogs. 2MASS J16411927-4047323, formerly proposed at the IR counterpart, is 6" from the Chandra position and Tomsick et al, therefore, refute this latter source as being the counterpart. More details in Tomsick et al. 2011 ATel 3342 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#470 5 May 2011 |
Bozzo et al. 2011 ATel 3326 report the results of 2 Swift follow up
observations of IGR J19149+1036.
In both observations a single point source is detected within the INTEGRAL error box. The best coordinates the authors obtain are RA=19h14m56.73s Dec = +10:36:38.11 (+- 3.7") with is still consistent with an association with the Einstein source 2E 1912.5+1031. The XRT spectrum is well represented by and absorbed power-law (N_H=6.5E+22 cm-2, Gamma=1.8). 2MASS J19145680+1036387 (J=14.34, H=12.41, K=11.53) is identified as the most likely counterpart to the source. More details in Bozzo et al. 2011 ATel 3326 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#469 4 May 2011 |
Scaringi et al. 2011 (A&A, 530, A6, arXiV 1012.1867)
report the results of their optical observations of the candidate IP 1RXS J165443.5-191620
also named IGR J16457-1916.
They detect modulations at 546s (compatible with the previously reported 549s ones) interpreted as the spin period of the compact object, and at 3.7h interpreted as the orbital period of the binary system. These are typical of CV/IP and these results therefore confirm the previously suggested nature of this source. The authors further remark that hard X-ray emitting IP later identified through optical spectroscopy all have SpinP<30 min and SpinP/OrbP < 0.1 The authors further discuss their findings More details in Scaringi et al. 2011 arXiV version at arXiV 1012.1867 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#468 20 April 2011 |
Altamirano et al. 2011 point new similarities
between IGR J17091-3624 and the famous microquasar
GRS 1915+105.
First: the 'heartbeat' oscillations were observed in all (but 3) observations performed since March 19th 2011. The authors report that the frequency of the oscillations has increased with time reaching ~100 mHz on April 18th, 2011. The increase of the frequency is also associated with a loss of regularity. In an observation performed on April 19th, 2011 a broad variety of complex behavior is seen. The type of variability in this date is similar to the class "beta" light curves seen in GRS 1915+105 although the timescales are different in the IGR. Altamirano et al. also mention that (similarly to 1915+105) QPO at 5-8 Hz occurring only during low intensity periods are also seen during this observation. More details in Altamirano et al. 2011 ATel 3299 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#467 20 April 2011 |
Malizia et al. 2011 ATel 3294, report the results of a Swift follow up
observation of IGR J08262-3736.
By obtaining an X-ray position of R.A. = 08h 26m 13.87s Dec.(J2000) = -37d 37m 11.03s (+-3.97 arcsec) they confirm the previously proposed association of the IGR with emitting line star SS188 and the X-ray source 1RXS J082615.4-373610. The IGR is therefore confirmed as an HMXB. The spectra is well fitted with an absorbed power law with Gamma ~ 2 NH~1.5 e22 cm-2 More details in Malizia et al. ATel 3294 Note that following the report of a possible nearby and 91s pulsating source close to H1743-322 (IGR J17464-3213) Motta et al. 2011 ATel 3295 analysed a recent Swift XRT photon counting mode observation of this field. They do not detect any other source within 12' from the BHC. They attribute the pulsation to H1743-322, and mention that such a phenomenon had already been seen in another BH source (GX339-4) More details in Motta et al. ATel 3295 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#466 19 April 2011 |
Malizia et al. 2011 ATel 3290, report the results of Swift follow up
observations of 2 IGRs.
IGR J11014-6103: One X-ray source is found within the IBIS error box at: RA = 11h 01m 46.4s Dec = -61d 01m 21s (+-6 ar csec). This is consistent with the position of 1RXH J110146.1-610121 and 2XMM J110147.1-61012. At other wavelengths, this source also coincides with USNO-A2.0 0225_10221381(R~14.7, B~16.2) and 2MASS J11014625-6101189 (J~13.9, H~13.6 and K~13.5). The Swift-XRT data are well fitted with a black body component with a temperature of ~85 eV plus a power law of photon index of ~2.6. IGR J14488-4008: two X-ray sources are found within the IBIS error box. Based on its characteristics the authors favour the following one: RA = 14h 48m 50.98s Dec = -40d 08m 47.12s (+-3.83 arcsec). This source is the brightest of the two. The X-ray position is consistent with the radio source CRATES J1448-4008 (NED03, F_(6cm)~126 mJy) NVSS J144851-400846 (F_(20 cm)~48 mJy). It also coincides with USNO-A2.0 0450_18513818 (R~14.0, B~14.7) and 2MASS J14485097-4008456 (J~16.7, H~12.7, and K~11.6). The XRT data are well fitted using a double power law model with indices tied together and with a value of ~2.4; Intrinsic absorption (Nh~7e22 cm-2) is found in addition to the Galactic absorption. More details in Malizia et al. ATel 3290 Tomsick et al. 2011 ATel report the discovery of the likely X-ray counterpart to IGR J15391-5307 with Chandra. While 5 sources are detected within the IBIS error box of the source, the authors favour the one that is closest to the centre of the error box, also the brightest of the 5, CXOU J153916.7-530815. It lies at RA = 15h 39m 16s.77 Dec = -53d 08' 15".9 (+- 0".64 @ 90%). This position is consistent with that of 2MASS J15391681-5308158 (H = 13.95 Ks = 12.99) DENIS J153916.8-530815 (J = 15.41, Ks = 13.06). The spectrum is not very well constrained but a fit with an absorbed power-law leads to Gamma ~ 3.6, and Nh~4e23 cm-2. The authors further discuss the potential nature of the source (HMXB vs AGN). While both types could show these spectral characteristics, they slightly favour an HMXB based on the location of the source close to the Galactic plane. More details in Tomsick et al. ATel 3293 The Maxi team reports on the new activity in X-rays from an unidentified source first associated to "PSR J1846-0258 or AX J1844.8-0258". They analysed their data further and saw that the source has been brightening since April 15, and the average flux is about 15 mCrab. The source position they obtain is RA= 18h 48m 19s, Dec=-03d 06' 36" . From all this they conclude that this transient is probably IGR J18483-0311. See the Maxi web sites and alerts here | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#465 12 April 2011 |
Testa et al. 2011 ATel 3264 report the possible identification of an IR counterpart to IGR J17480-2446. From ESO VLT observations the authors report the presence of two possible IR source within 0.3" of the Chandra position. They favor the one located at RA=17:48:04.829, DEC=-24:46:49.10 (+/-0.3"), with Ks = 16.6 as the candidate counterpart due to its absence in previous catalogues. More details in Testa et al. ATel 3264 Pahari et al. 2011 ATel 3266 report the presence of multiple peaks with evolving frequencies in the recent RXTE observations of IGR J17091-3624. They discuss their findings and compare them to the class rho of GRS 1915+105 More details in Pahari et al. ATel 3266 Landi et al. 2011 ATels 3271, 3272, and 3273 report the results of Swift observations of the field of 7 IGRs. For each they report the presence of X-ray potential counterpart(s) within the INTEGRAL error boxes and give their position. They also browse the multi-wavelengths archive and report, when appropriate, the association of the X-ray sources with source seen at other wavelengths. More details in ATel 3271, ATel 3272, ATel 3273. Rojas et al. 2011 ATel 3275 report the results of near Infra red observations of the field of IGR J17177-3656. They do not detect any source within the Chandra error of the source with limits of J~19.5, H~18.0 and K~18.0. They, however, remark the presence of two sources just outside the Chandra error box. From possible variations of the magnitudes of one of these objects the authors mention a possible association to the IGR More details in Rojas et al. ATel 3275 Finally Linares et al. 2011 accepted in ApJ, report an extensive analysis of all (373) the X-ray burst of IGR J17480-2446 as observed with RXTE. Their main conclusion is that all bursts have a thermonuclear origin (type I burst), even those without a cooling tail. Much more details can be found in Linares et al. 2011 arXiV 1102.1455 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#464 8 April 2011 |
Degenaar and WIjnands 2011 accepted in MNRAS report the results of a Chandra observations
of the 11Hz pulsar IGR J17480-2446, seven weeks after the end of
its 2010 outburst.
The main result is that they detect a thermal emission (~100 eV) from the neutron star that is elevated compared to the value (~70 eV) found during the true quiescence of the source. The authors interpret this finding as evidence for crustal heating during the outburst, while they dismiss other interpretation such as residual accretion onto the neutron star. They further discuss their results and add that this first evidence of crustal heating in a transient system with regular outburst will permit to have a new approach to the study of heating and cooling of neutron star crust. More details in Degenaar and Wijnands arXiV 1103.1640 Sidoli et al. 2011 accepted in MNRAS report the results of simultaneous INTEGRAL and XMM observations of the very faint transient IGR J17285-2922. The broad band spectrum of this source is well represented with an absorbed power law spectrum with Nh=0.5e22 cm-2 and Gamma=1.61. No cut off is required in the fit and the authors can set a lower limit to Ec > 50 keV for a potential cut off. No type I X-ray bursts or coherent pulsations are found. The temporal analysis of the source shows that the power spectrum has a shape typical of that of LMXBs in the low hard state and a level of variability (20% between 0.1 and 1 Hz) also compatible with this interpretation. The authors discuss their results and conclude that the source is an LMXB, possibly hosting a black hole, although they cannot clearly conclude on the true nature of the compact object. More details in Sidoli et al. arXiV 1104.1055 H1743-322 (aka IGR J17464-3213) is currently in outburst as reported by Kuulkers et al. 2011 (ATel 3263) and us (Rodriguez et al. ATel 3267) from INTEGRAL observations. The source is currently in the hard state and has been continuously rising in flux since the moment of its first detection by INTEGRAL. Further observations are planned More details in Kuulkers et al. ATel 3263 and Rodriguez et al. ATel 3267 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#463 5 April 2011 |
Ibragimov et al. 2011 accepted in MNRAS report an in-depth analysis
of the 2009 outburst of IGR J17511-3057 based on Swift and RXTE observations.
The spectra of the source are well fitted with a model of Comptonization (from the accretion shock) with kTe~30 keV and tau~2, plus a black body (from the NS hot spot) with kT~1 keV. The Swift/XRT spectra show in addition the presence of a cold disk (~0.2 keV) while they can estimate an absorption Nh~0.9e22 cm-2. Weak reflection component and an iron line are also detected. The authors remark that both the area of the BB emission associated to the hot spot and the eq. Width of the iron line decrease during the outburst. The authors also present an analysis of the temporal properties and mention that the pulse profile do not evolve significantly in shape, and show a moderate decrease in pulse amplitude. The time lags between the soft and hard pulses, however, increase during the outburst. Ibragimov et al. present an interpretation of these results and mention in particular that the behavior of the lags could be for example due to a displacement of the accretion shock relative to the hot spot. Much more details including a deeper discussion on these aspects can be found in Ibragimov et al. 2011 arXiV 1102.1909 Fiocchi et al. 2011 ATel 3256 report the results of Swift follow ups of two IGRs. IGRJ12470-5407: Only one source is found within the 99% IBIS error box at: R.A. = 12h 47m 50.80s Dec. = -54d 06m 30.80s (+-5 arcsec) No counterparts were found when searching the archives in other energy bands. IGRJ18532+0416: 2 objects are detected within the 99% IBIS error box: The favoured counterpart (because it is the only source detected at >3 keV) is located at RA=18h 53m 16.3s Dec.= +04d 17m 50.6s (+-5 arcsec) 2 candidates counterparts are found within the X-ray error box: 2MASS18531638+0417540 and 2MASS18531602+0417481 with J ~16.5, H ~14.1, K ~14.4 for the former and J ~16.5, H ~14.1 and K ~13.9, for the latter. See Fiocchi et al. for more details ATel 3256 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#462 30 March 2011 |
Corbel and Tzioumis 2011 ATels 3246,3247 report the discovery of
a radio source within the Chandra error box of IGR J17177-3656.
The position of the source is RA = 17h 17m 42.59s Dec= -36deg 56' 04.4" (+-0.5"). The measured flux densities are ~0.24 mJy at 5500 MHz and ~0.20 mJy at 9000 MHz. The constrains on the spectral index is rather poor (alpha = -0.37 +/- 0.79), and the radio spectrum could therefore either be indicative of a compact jets or a discrete ejection event. Corbel and Tzioumis further discuss the implication of their findings, and mention that IGR J17177-3656 could be a BH in a hard state, or the the radio may be resudual radio emission from a discrete ejection. More details in Corbel and Tzioumis ATel 3246 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#461 29 March 2011 |
Torres et al. 2011 ATel 3241 report some results of IR
observations of the field of IGR J17177-3656.
They first report that they do not find any counterpart within the Chandra error box of the source. They do discuss the possible association of the 2MASS source lying 1" from the position of the IGR and rule it out based on its colour. They also mention the presence of a faint source seen in their images also at 1" from the IGR position, and rule it out based on the separation to the X-ray source. They conclude that the counterpart to the IGR may have not been brighter than 17.5 mag (in Ks band) at the time of their observations. More details in Torres et al. ATel 3241 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#460 24 March 2011 |
The currently-active X-ray transient and black hole candidate, IGR J17091-3624,
was previously seen in archival VLA observations of the field. The average radio
position of R.A. (J2000)=17h 09m 7.6s (+- 0.3s) and Dec.= -36d 24' 23.3" (+- 3.1")
is consistent with both the ATCA and XRT positions. The flux densities are between
0.6 and 1 mJy at 5 and 8.5 GHz.
Please see Bietenholz et al. (2011, ATel #3232):
ATel 3232
The SFXT IGR J17544-2619 underwent a new outburst. At 50 cps in the XRT, this outburst
is about twice as bright as previous ones, the last of which was observed a year ago
(Romano et al. 2011). This is attributed to Swift reacting rapidly and slewing to the
source during an early part of this outburst.
More information can be found in Romano et al. (2011, ATel #3235)
ATel 3235
Paizis et al. (2011) report the Chandra position for the recently-discovered transient IGR J17177-3656:
R.A. (J2000) = 17h 17m 42.62s Dec. = -36d 56' 04.5" error = 0.6" This position is consistent with the JEM-X position but is 4.8" from the XRT position (which has a 2.1" error radius). It also rules out both of the previously-proposed 2MASS counterparts. The parameters f rom MEG/HEG first-order average spectra are nH=5.9(1.5)e22 /cm2 (larger than the expected absorption through the Galaxy) and Gamma=1.2(4). The 2--10-keV flux is 6.2e-11 erg/cm2/s (~3 mCrab). Please see Paizis et al. (2011) for more information: ATel 3236 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#459 23 March 2011 |
From their analysis of recent INTEGRAL observations the Galactic Bulge,
Kuulkers et al. (2011, ATel: 3229) conclude that IGR J17098-3628 is unlikely to
be the source of the 10 mHz QPOs (ATel: 3225). Recall that the QPOs are tentatively
assigned to IGR J17091-3624, but the angular resolution of RXTE/PCA does not permit the
exclusion of IGR J17098-3628 as the QPO source (ATel: 3225). While IGR J17091-3624 continues
to be active in the X-rays (detected by both JEM-X and ISGRI at the 28 and 58 mCrab level, respectively),
IGR J17098-3628 is not detected by either instrument (nor is it seen by Swift/XRT, see below).
Thus, the mHz QPOs are confidently attributed to IGR J17091-3624.
Furthermore, Altamirano et al. (2011, ATel: 3230) report that these mHz QPOs have increased
in frequency by a factor of ~3. The PCA light curve of IGR J17091-3624 displays flaring events occurring
at a rate of 25-30 mHz, with a wide diversity in the flare profiles (FRED flares, single and double-peaked
flares). These flares are also observed with Swift/XRT (which did not detect IGR J17098-3628). Such high
frequencies are inconsistent with those of accreting neutron stars, but they are reminiscent (while of
lower flux) of the "heartbeat" oscillations seen in the black hole candidate GRS 1915+105.
For more information, please see Kuulkers et al. (2011, ATel: 3229) and Altamirano et al. (2011, ATel: 3230):
ATel 3229 and ATel 3230 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#458 18 March 2011 |
Altamirano et al. 2011 ATel 3225 report the discovery of
a 10 mHz QPO most likely from IGR J17091-3624.
The QPO is only intermittently visible with an average 2-60 keV fractional rms amplitude of 5.3+-0.4% and a mean frequency of ~10 mHz. The fractional rms amplitude increases from ~3.5% below 5 keV to a maximum of ~10% in the 15-30 keV range. The authors also report that In the same observation two QPOs at 2.3 Hz and 8.0Hz, with fractional rms amplitudes of 10.9% and 6.7%, are found More details in Altamirano et al. 2011 ATel 3225 Zhang et al. 2011 ATel 3226 report the results of Swift observation of IGR J17177-3656 and their identification of potential counterparts at other wavelengths The swift pointing permitted the X-ray position to be refined to RA = 17h17m43s, Dec = -36deg 56' 03" ( ±2.1 arcsec). This position is about 2' from the putative counterpart previously proposed ruling out any association between the two sources. The author present the results of spectral analysis of two pointings which show no significant evolution of the parameters. An absorbed powerlaw fits the data well with N_H = 3.7 e22 cm-2 and Gamma = 1.45. The authors report the presence of 2MASS J17174269-3656039 with J=15.2, H=13.9 and K=12.9 also present in the NOMAD and GLIMPSE catalogs within the Swift error box. A radio source from the 1.4 GHz NRAO VLA Sky Survey NVSS J171743-365606 is also found at a position consistent with that of the X-ray source More details in Zhang et al. 2011 ATel 3226 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#457 17 March 2011 |
Frankowski et al. 2011 ATel 3223 report the discovery of a new INTEGRAL source
IGR J17177-3656 in observations covering the period 2011-03-15 09:23
to 2011-03-15 22:42 UT.
The source was detected by IBIS/ISGRI and marginally in a 10-20 keV mosaic of the two JEM-X units. The IBIS/ISGRI position is RA = 17h 17m 39s Dec = -36deg 56' 17" (± 2.2 arcmin) Jem-X allows a slight refinement to RA=17h 17m 46s Dec=-36deg 56' 42" (±1.5 arcmin) The IBIS/ISGRI spectrum (20-150 keV) can be well described by a power-law with Gamma~1.8 During subsequent INTEGRAL observations the source is seen at a slightly higher flux suggesting an increasing luminosity trend. The authors add that a Swift/XRT pointed observation of the field performed on 2011-01-27 did not yield a detection with a 1-10 keV 3 sigma upper limit of 1.5e-12erg/s/cm2 More details in Frankowski et al. ATel 3223 Further to that Malizia et al. 2011 ATel 3224 mention the presence of the H-alpha emission star 2MASS J17175282-3655550 ([KW2003] 9) at the following coordinates RA: 17h 17m 52.84s , Dec: -36d 55m 56.2s ie slightly outside of the IBIS and JEMX error boxes. The star is also listed in several optical and near-infrared catalogues with J=10.68, H = 10.21, K = 9.90, R = 13.3 and B = 14.4, and the following mag in the GLIMPSE catalogue 5.8 um = 9.5 and 8.0 um = 9.0. The authors think that the IGR and the star may be associated More details in Malizia et al. 2011 ATel 3224 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#456 4 March 2011 |
Nichelli et al. 2011 report the discovery of coherent
X-ray pulsations in IGR J17200-3116 detected by Swift-XRT at
a period of 328.182(3) s with a derivative of 1.5e-8 s/s. While the pulsation period was not detected in a 5-ks Chandra observation from 2007, the periodicity was detected in the 18-30 keV band in archival INTEGRAL-ISGRI observations from 2003 to 2006. This confirms that IGR J17200-3116 is an accreting pulsar in an HMXB system. More information can be found in Nichelli et al. ATel 3205 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#455 3 March 2011 |
Del Santo et al. 2011 ATel 3203
report the results of
Swift and INTEGRAL observations of the BHC IGR J17091-3624
performed on Feb 28, 2011.
The authors first fitted the XRT data alone, and mention the need for a disc in the best fit model. The fit of the joint 0.8-200 keV XRT+IBIS/ISGRI spectrum is well represented by an absorbed disc + powerlaw with N_H~1.00, kT_disc~1.0 keV and Gamma~ 2.2. No high-energy cut-off is requested up to 200 keV. The estimated fluxes in the 2-10 keV and 20-100 keV energy bands are 2E-09 erg/cm^2/s and 9E-10 erg/cm^2/s, respectively. The authors conclude that IGR J17091-3624 is presently in the canonical high/soft spectral state of BHCs More details in Del Santo et al. 2011 ATel 3203 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#454 2 March 2011 |
Romano et al. 2011 ATel 3200 report preliminary results
of a Swift observation performed at the expected moment of
a peak of outburst of the SFXT IGR J11215-5952 (on 2011 March 1).
The source was detected and the spectrum can be fitted with an absorbed powerlaw model with Gamma~1.0 and NH~2.2E+22 cm-2 The authors add that all their findings are consistent with those of previous outbursts More details in Romano et al. 2011 ATel 3200 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#453 1 March 2011 |
Miller et al. 2011 describe their analysis of Chandra/HETG spectra
(30 ks total exposure time) of the transient LMXB pulsar in Terzan 5: IGR J17480-2446.
They detect blue-shifted absorption lines from helium-like Fe XXV and hydrogen-like Fe XXVI. These suggest the presence of an accretion disk wind which does show strong variations with X-ray bursts or flares. This may represent the clearest detection yet of such a wind in a neutron star system. The authors propose that the inner accretion disk is radially-truncated given their results from model fits to the broad Fe K emission line. This indicates a stellar magnetic field strength of ~(1-4)x10^9 G. For more on where these results fit in the context of accretion onto compact objects, and for a discussion on how the disk winds of IGR J17480-2446 might differ from those seen in stellar-mass black holes, please see Miller et al. (2011) accepted in ApJL: arXiV 1101.2377 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#452 25 Feb. 2011 |
Landi et al. 2011 ATel 3184 and 3185 report the results of Swift follow up
observations of IGR J14043-6148, J06523+5334, J18371+2624 and identifications of counterparts
at other wavelengths.
IGR J14043-6148 An X-ray source is found within the IBIS error. It is also significant above 3 keV. This object lies at: R.A. = 14h 04m 29.63s Dec. = -61d 47m 19.7s (±4.5 arcsec ). USNO-B1.0 0282-0474947 (R ~18.5, B ~20) also reported in the 2MASS/GLIMPSE catalogue (J=16, H=13, K=11 and M(8um) = 8 mag) is found at a position consistent with the X-ray source. A non thermal radio source (G311.45-0.13) with F(6cm)= 0.5 Jy is also compatible with the X-ray object. This object is slightly resolved and has been proposed to be either a small SNR or a background galaxy. Based on the X-ray characteristics, the authors favor an AGN nature for the object, although a composite SNR/pulsar wind nebulae cannot be excluded. IGR J06523+5334: Two sources are found within the 90% IBIS positional uncertainty: The authors favour the first, brightest and only one detected above 3 keV as the counterpart to the IBIS source. It is located at R.A. = 06h 52m 31.35s Dec. = +53d 31m 26.2s (±4.7 arcsec ). This is compatible with 1RXS J065230.8+533130 and also QORG J065231.2+533130 (in optical) a QSO candidate with B=18.3 and R=17.7. It is also detected in 2MASS catalogue with J ~17, H ~16 and K ~15. The X-ray spectrum is well fitted by a power law with Gamma=1.8 IGR J18371+2634: One source is found at border of the 90% error circle another one inside the 99% uncertainty region. The authors dismiss source 2 as the counterpart due to its softness. The preferred counterpart is located at R.A.= 18h 37m 28.7s Dec. = +26d 32m (±6 arcsec ). This is compatible with the position of 1RXS J183728.8+263225 and a 2MASS object with J ~11, H ~10 and K ~10, also detected in optical with B ~14 and R ~13. More details in Landi et al. ATel 3184 and ATel 3185 Further to that Halpern 2011 ATel 3186 observed the suggested optical counterpart of the favour X-ray coutnerpartt to IGR J06523+5334 (in USNO B1.0 at R.A. = 06h 52m 31.407s, Decl. = +53d 31' 31.55") with B2 = 18.80, R2 = 18.12, I2 = 17.57. He reports detection of [O III] 5007,4959 and broad Balmer emission lines at z = 0.301. This indicates that this broad-line QSO is a possible identification of IGR J06523+5334. AT this distance the 2-10 keV luminosity of the source is ~5.e43 eeg/s More details in Halpern ATel 3186 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#451 24 Feb. 2011 |
D'Ai et al. 2011 accepted in MNRAS report the results of their analysis of Swift
observations of 3 IGRs. The source in question are IGR J0507-7047, J13186-6257
and J17354-3255.
For each source the authors search the longterm BAT light curves for periodicity (interpreted as the orbital periods of these 3 HMXBs) and study joint XRT+BAT data. The main results can be summarized as follows: J05007-7047: A 30.77d periodicity, consistent with previous reports, is found in the BAT lc. The XRT pointings occur on three different orbital phases. Only the one obtained around phase 0.47 has a sufficient number of counts to perform a spectral analysis. The spectrum is weel represented by an absorbed (>0.17e22 cm-2 interstellar) power law (Gamma=0.3) with a cut-off (Ec=12 keV). J13186-6257 A periodicity is found at 19.99 d. The XRT pointings occur during two phases. The source is clearly detected in one, and not in the other pointing. The spectrum is well fitted by an absorbed (NH = 17e22 cm-2) power law (Gamma=2.3), even if the authors mention that the normalization constant between XRT and BAT is very low and could indicate very large variation. They discuss the implications of their results and favor a Be-HMXB. J17354-3255 A significant periodicity is found at 8.448 d. The XRT observations cover two phases, one near the minimum (of the folded lc) one near the maximum. Two possible counterparts are seen in the IBIS error box. Due to the non-detection of the favored one at the expected phase of lowest activity, the authors associate further associate it to the IBIS source. The spectrum is well fitted by an absorbed (NH = 10.6e22 cm-2) power law (Gamma=2.6). Adding a cut off improves the fit and slightly modify the parameters. The cut off is poorly constrained (>18 keV). More details in Dai et al. 2011 arXiV 1102.4546 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#450 22 Feb. 2011 |
Landi et al. 2011 ATel 3178 report the results of a refined analysis of the Swift/XRT of
IGR J16413-4046.
A new Swift observation of this source yields a better detection significance, and leads
to a refined, and more precise X-ray position of the source: RA= 16h 41m 19.19s Dec. = -40d 47m 36.6s (± 5.6"). The X-ray spectrum is well fitted with an absorbed power law (Gamma = 1.8, NH ~ 1E23 cm-2) More details in Landi et al. ATel 3178 Shaposhnikov 2011 ATel 3179 report further results on the RXTE observations of IGR J17091-3624. He observes fast evolution of the QPO seen in this source. The formerly reported 0.1 Hz QPO is observed at 0.34, 0.45 and 1.66 Hz in the three most recent observations (Feb 18,19 and 20, 2011). A QPO harmonic is also observed at ~3.3 Hz in the last observation. Although no spectral analysis is possible, the hardness is seen to decrease, indicating that the spectrum of IGR J17091-3624 is getting softer. Shaposhnikov concludes that this behavior is consistent with the source making a transition to the soft state, with a possible transition to the soft intermediate state within a few days. More details in Shaposhnikov 2011 ATel 3179 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#449 18 Feb. 2011 |
Papitto et al. 2011 accepted in A&A report the analysis of RXTE observations
of the ms accreting pulsar IGR J00291+5934. Based on these data they
estimate the neutron star spin (~598.892 ms) over 3 period of observations (2004,
2008a and 2008b outbursts), refine the orbital solution of the system, measure
spin up of the source during outbursts, and discover that the source spins down
during period of quiescence (average rate -4.1e-15 Hz/s).
They discuss this specific finding in the context of various models, and favour
one based of magneto dipole emission as the origin of the spin down.
In this framework they estimate an upper limit to the magnetic field B<3e8 G.
More details in Papitto et al. 2011
arXiV 1006.1303
Romano et al. 2011 ATel 3174 report the results of a Swift follow up
observation of IGR J16418-4532, triggered after the MAXI Nova
alert 5609524433 (see http://maxi.riken.jp/alert/novae/5609524433/5609524433.htm ,
Note that this alert was canceled later, and the alert due to GX 340+0).
They first refine the X-ray position to RA(J2000) = 16h 41m 50.74s, Dec(J2000) = -45d 32m 23.9s, (±2.3" @ 90% confidence). The light curve shows the decaying portion of a flare that reached 3 counts/s, with a dynamic range of about 70. The spectrum can be fitted by an absorbed power-law with Gamma= 2.0 NH=8E22 cm-2. By comparing these results to the XMM one published in 2006, the authors conclude that the source is quite bright, and add they may simply have caught one of the flares typical of SFXTs More details in Romano et al. 2011 ATel 3174 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#448 16 Feb. 2011 |
Corbel et al. 2011 ATel 3167 mention that the ATCA
data around IGR J17091-3624 indicates the presence of a single radio
source within the X-ray error circle, at RA= 17:09:07.61 Dec = -36:24:25.6 (±0.1"), also consistent with the optical counterpart. The flux densities of ~1.3 mJy at 5.5 and 9 GHz are consistent with a flat radio spectrum, usually associated self absorbed compact jets. They also fitted the Swift XRT spectra closest to the radio observation, and found the following parameters: 2011-02-09 N(H) = 0.72E22 cm-2, Gamma = 1.41 2011-02-10 N(H) = 0.74E22 cm-2, Gamma = 1.52 These parameters, and the inferred luminosity (projected at 8 kpc) places IGR J17091-3624 in between the standard track in the radio/X-ray correlation diagram and the track that could possibly be indicative of a radiatively efficient black hole in the hard state. Rodriguez et al. 2011 ATel 3168 report the results of timing analysis of 4 RXTE/PCA observations. They remark that the data are contaminated by the nearby source GX 349+2, but manage to roughly correct its influence. All PDS but the one from the first observation show the presence of a ~0.1 Hz QPO, with an increasing RMS amplitude (from 3.2% to 4.5%). They attribute this QPO to IGR J17091-3624. The results presented in both ATel lend further credence to the fact that IGR J17091-3624 is a black hole binary in a hard state More details in Corbel et al. 2011 ATel 3167 and Rodriguez et al. 2011 ATel 3168 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#447 15 Feb. 2011 |
Gotthelf et al. 2011 accepted in ApJ report the results of
observation of IGR J18490-0000 with XMM and RXTE.
Inspection of the XMM data allows these authors to find a bright source, XMMU J184901.6-000117, that they associate with the IGR source. They remark the presence of extended emission that they interpret as suggestive of the presence of a PWN. They then study the spectra of the point like source and of the extended component. The point like source has a hard spectrum (Gamma=1.1) while the extended component is softer (Gamma=2.1) both absorbed with Nh=4.3e22 cm-2. Gotthelf et al. also report the discovery of a period at 38.52 ms seen in the RXTE data, indicative of a pulsar at the centre of this source. This allows them to estimate the following parameters for the pulsar: spin-down luminosity: 9.8e36 erg/s (assuming d=7kpc) characteristic age: 42.9 kyr surf. dip. magnetic strength: 7.5 e11 G More details in Gotthelf et al. 2011 arXiV 1012.2121 Gangopadhyay et al. 2011 accepted in New Astronomy estimate the mass and compactness of several neutron stars based on the differences between their kHz QPOs. One of these sources is IGR J17191-2821 for which the mass is estimated at 0.843 Msun, and the radius 6.762 km. More details in Gangopadhyay et al. 2011 arXiV | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#446 12 Feb. 2011 |
Capitanio et al. 2011 ATel 3159 report the detection of the BHC
IGR J17091-3624 with both JEM-X and IBIS/ISGRI during recent
observation of this region.
The combined ISGRI+JEMX2 spectrum (5-300 keV) is well described by an absorbed cut-off power law with Nh frozen to 1.1e22 cm-2, Gamma=1.4 Ecut= 110 keV The authors conclude that the source is currently in the hard state More details in Capitanio et al. ATel 3159 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#445 10 Feb. 2011 |
Torres et al. 2011 ATel 3150,
report the detection of the optical and near-infrared
counterparts of IGR J17091-3624
They find an I = 18.35 mag point-like source within the Swift error box at R.A =17:09:07.62, Dec =-36:24:25.35. while in the 2005 images this object had I = 20.32. In NIR the authors report the detection of a Ks=16.65 source consistent with the optical counterpart. The finding chart can be found at http://hea-www.cfa.harvard.edu/~mtorres/IGRJ17091m3624.html (courtesy M.A.P. Torres) More details in Torres et al. 2011 ATel 3150 Motta et al. 2011 accepted in MNRAS report a study of the morphological, spectral and temporal properties of the bursts of the recent X-ray pulsar IGR J17480-2446 (Terzan 5) as observed by RXTE. They remark that the recurrence time and the fluence of the bursts clearly anticorrelate with the increase of the persistent X-ray flux. The ratio between the energy generated by the accretion of mass and that liberated during bursts indicate that Helium is ignited in a Hydrogen rich layer. One of the first conclusions drawn is that all the bursts of this source are Type-I X-Ray bursts. Motta et al. also detect pulsations in all the brightest bursts with no drifts of the frequency within 0.25 Hz of the spin frequency of the pulsar. Based on their analysis the authors favour a scenario where the flash is ignited within a region as large as the neutron star surface. Much more details in Motta et al. 2011 arXiV 1102.1368 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#444 7 Feb. 2011 |
Krimm & Kennea 2011 ATel 3148 report the result of
a Swift observation of a field containing both IGR J17091-3624
and IGR J17098-3628. While no flux is detected from the latter, IGR J17091-3624 is strongly detected in the XRT image. The spectrum is well represented by an absorbed power law with NH = 1.10 E22 cm-2 and Gamma = 1.73 +/- 0.29 The source is not detected by UVOT. More details in Krimm and Kennea ATel 3148 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#443 4 Feb. 2011 |
Krimm et al. 2011 ATel 3144 report the detection of increased
activity from the black hole candidate IGR J17091-3624 with
Swift/BAT.
The source has increased from a normal average intensity of ~3 mCrab up to to 20 mcrab on 28 Jan 2011 and further up to 60 mcrab by 03 Feb 2011. The author also mention that another BHC (IGR J17098-3628) is located 8.5 arc minutes away and that since the BAT PSF for the two sources overlap, they cannot definitively determine which source is in outburst from the BAT data alone, although they seem to favour IGR J17091-3624. More details in Krimm et al. 2011 ATel 3144 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#442 28 Jan. 2011 |
Rodriguez et al. 2011 ATel 3125, report the refinement
of the positions of two IGRs using XMM-Newton.
Although the Sey 1 AGN IGR J18027-1455 has been well studied no fine X-ray position is reported anywhere. We found only one bright X-ray counterpart within the IBIS error. The best X-ray position is RA = 18h 02m 47.32s Dec = -14deg 54' 54.6" (±3.4" at 90%) This position is compatible with all previously suggested counterparts, including (at the 2-sigma level) compatible with 1RXS J180245.5-145432. IGR J19284+0107: A single X-ray source is found just on the outer edge of the IBIS 90% error box at: RA=19h 28 29.6s Dec=+01deg 06' 42.4" (± 3.8" at 90%). We did not find counterparts in the Rosat, 2MASS, 2MAS X, NVSS, USNO-B1.0, and NED catalogues within the XMM-Newton error box. 2MASS J19282921+0106418 (J=15.9, H=15.7, Ks=15.3) and USNO-B1.0 0911-0445937 (B=18.2, R=16.4, I=16.7) lie at respectively 5.8" (at ~2.6 sigma) and 5.4" (2.4 sigma) from the X-ray position and could be associated with it. We do not exclude a chance association of the X-ray and IGR sources. More details in Rodriguez et al. 2011 ATel 3125 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#441 17 Jan. 2011 |
Walter et al. 2011 ATel 3108, report the discovery of a new source IGRJ12580+0134
with INTEGRAL/IBIS, and also detected with JEM-X.
A Swift XRT TOO follow-up observation allowed them to confirm that the IGR was
associated with with the central regions of
NGC 4845 with X-ray coordinates RA=194.5048 DEC=1.5753 (+/-3.6 arcsec, J2000). The Swift XRT spectrum can be modeled with an absorbed (Nh ~ 8E22 cm-2) powerlaw (gamma ~ 3.3+/-0.3). The source is therefore a flaring Seyfert 2 galaxy. More details in Walter et al. 2011 ATel3108 Kalamkar et al. 2011 accepted in ApJ, report the possible discovery of twin kHz QPOs in the accreting ms pulsar IGR J17511-3057 with RXTE. From analysis of the colour-colour diagrams and power spectra, they first mention that the behaviour of this source is similar to that of Atoll NS-LMXBs. in this respect the source spent its outburst in the extreme Island state. They remark that contrary to other such sources, the frequency difference between the two kHz QPO is consistent with half the spin frequency of the NS, a behaviour usually seen in fast rotators. Their results point towards IGR J17511-3057 being a peculiar source , and the authors insist that it could play an important role in the understanding of kHz QPOs in NS LMXBs and AMPs. More details including discussions on the possible origin of these QPOs can be found in Kalamkar et al. 2011 arXiV 1101.2680 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#440 06 Jan. 2011 |
Degenaar & Wijnands 2011, accepted in MNRAS report the analysis
of archival Chandra data of the field around IGR J17480-2446 in
Terzan 5, when the source was inactive.
They study the quiescent spectra of the source, and found no difference between the 2 observations. The spectra are soft with most photons detected below 2 keV. Fitting the spectra with a model of an absorbed NS atmosphere yields a good chi square and the following parameters NH = 2.1E22 /cm2 and kT= 72.7 eV. The authors discuss their results, starting with a comparison of the spectral properties of this source during quiescence with 5 other accreting ms pulsars. By estimating the duty cycle of the source they estimate that this source has spent > 100 years in quiescence. Although a low duty cycle is possible another explanation for the low quiescent luminosity of this source is suggested; an enhanced neutrino emission mechanisms could cool the neutron star down to the observed quiescent luminosity. The authors further discuss the implications of such a scenario. More details in Degenaar and Wijnands 2011, arXiV 1101.0842 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#439 04 Jan. 2011 |
This new year of IGR emails starts with a paper on the origin of the
IGR J17480-2446's bursts by Chakraborty and Bhattacharyya (accepted ?) in
ApJ (?).
The authors have analysed the whole RXTE/PCA data set finding a total of ~400 X-ray bursts for which they studied the spectral properties of the source during the bursts. They first conclude that all the bursts from the source originate from the same mechanism, and that they have a thermonuclear origin. They mention that a clear cooling may not always be present during a thermonuclear burst decay. Finally the source is not analogous to GRO J1744Ð28 More details in Chakraborty and Bhattacharyya arXiV 1101.0181 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#438 16 Dec. 2010 |
Corbet and Krimm 2010 ATel 3079 report the discovery of a 160 day period
in the Swift/BAT light curve of the Be XRB IGR J01363+6610.
The authors add that this modulation is only present in recent data.
They parametrize the modulation with a sine wave and obtain from their fit: Tmax = MJD 55,291 +/- 3 + n x 159 +/- 2 where Tmax is the time of maximum flux. (only from data afer MJD 54 750) The authors further discuss this modulation in terms of an orbital period, and although 160 d would be consistent with a Be XRB, they mention that only a small number of 160 day cycles are covered during the apparent active state and therefore this interpretation should be taken with caution. More details in Corbet and Krimm ATel 3079 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#437 15 Dec. 2010 |
Landi et al. 2010 ATel 3708 report the results of Swift observations
of the field of 3 IGRs.
IGR J02115-4407: 3 X-ray sources are found within the IBIS error box, but none of them emits above 3 keV. Only the first one has clear counterparts at other wavelengths, and is associated with a galaxy. The authors conclude that all three X-ray sources are most likely associated with the galaxy group LCLG-45078 at z = 0.104. The nature of the IBIS source is not clear for them. IGR J16443+0131 A single X-ray source is found within the IBIS error box at RA = 16h 44m 38.1s Dec= +01d 29m 03.5s (±6 "). A USNO-B1.0 (R ~18.5, and B ~20),and 2MASS objects (J ~16.8, H ~15.9, and K ~15.1) have position consistent with the X-ray one. This is also compatible with NVSS J164437+012903 that has a 20 cm flux of 7.2 mJy. The authors suggest that this source is an AGN. IGR J18457+0244 1 X-ray source is detected in the IBIS error, even at energies > 3 keV. It is located at RA= 18h 45m 40.1s Dec. = +02d 42m 07.3s (±6 "). Two 2MASS objects with similar magnitudes ( J ~16, H ~15, and K ~15) are found at this position. More details in Landi et al. 2010 ATel 3078 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#436 14 Dec. 2010 |
Tomsick et al. 2010 accepted in ApJ, report
XMM, Optical/IR and Chandra analysis of the field of IGR J01363+6610.
Using the updated IBIS position for this source they find 7 X-ray
objects in both XMM and Chandra observations within the
IBIS error box.
One of this source is consistent with the Be star that was formerly proposed
as the counterpart, confirming that this object is also an X-ray source.
The analysis of all the available data, starting with the optical spectra,
leads the authors to conclude that this source is, indeed, the counterpart
to the IGR.
The X-ray spectra are well fitted with an absorbed power law with Gamma=1.4 and Nh=1.5e22cm-2.
The authors then estimate the quiescent luminosity based on their previous
Chandra observation, and show that the source has a very low luminosity
compared to other sources.
They discuss different possibilities for this low luminosity, including the possibility that IGR J01363+6610 is a Be-binary with a black hole, or that it has a large circular orbit. More details in Tomsick et al. 2010 arXiV 1012.2817 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#435 9 Dec. 2010 |
Bodaghee et al. 2010 report on a 37-ks Suzaku observation of the SFXT IGR J17391-3021
(=XTE J1739-302). During the first half of the observation, the source was in a dormant state
equivalent to quiescence with an absorbed luminosity of 1.3e33 erg/s (d/2.7 kpc)^2. During the second half of the observation, the source entered a low-activity state punctuated by weak flares in which the peak luminosity of 7.4e33 erg/s is only a factor of 5 times that of quiescence. During the weak flaring phase, the column density (~4.1e22 /cm2) represents an increase of a factor of 2--4 (compared to the value measured during quiescence) suggesting the accretion of obscuring clumps of wind. When this observation is placed in the context of the year-long Swift monitoring program, we find that this low-activity state is at the level of the lowest detections (and some upper limits) from Swift. Representing 60+-5% of all observations, we now recognize this low state as the most common behavior in this source. For more, please see Bodaghee et al. (2010, accepted by ApJ): arXiV 1012.0855 A reanalysis of the field around AX J1910.7+0917 by Pavan et al. (2010) revealed 3 new IGR sources (some of which were followed up by Swift). Their details are provided below: IGRJ19173+0747: R.A. (J2000): 19:17:20.8 Dec.: 07:47:51.1 Error radius: 3.8 arcsec (Swift-XRT), ISGRI detection significance: 10.0, nH: <6e21 /cm2, Gamma: 0.6(2) (0.5--10 keV) and 3.3(9) (17--80keV). Probable counterpart: 2MASSJ19172078+0747506 IGRJ19294+1327 R.A.: 19:29:29.8 Dec.: 13:27:05.4 Error radius: 5.0 arcsec (Swift-XRT), ISGRI detection significance: 6.8, Possible counterparts: 2MASS J19292976+1327087 and 2MASS J19293011+1327056 IGRJ19149+1036 R.A.: 288.73 Dec.: 10.6 Error radius: 1.0 arcmins (ISGRI), ISGRI detection significance: ~20, Comments: Coincident with 2E1912.5+1031. Values are affected by systematic uncertainties related to the presence of GRS 1915+105 nearby. Please see Pavan et al. (2010, accepted by A&A): arXiV 1012.1164 Bikmaev et al. (2010) present the optical identification of IGR J21565+5948 by the Russian-Turkish Telescope. They identify the counterpart as the Sey-1 AGN labeled 2MASS J21560418+5956045 (=USNO-B1.0 1499-0325257) with coordinates R.A. (2000) = 21:56:04.202 and Dec. = +59:56:04.46. A finding chart is available in Bikmaev et al. (2010: ATel:3072): ATel 3072 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#434 6 Dec. 2010 |
Landi et al. 2010 ATel 3065 report the results of Swift observations
of the field of two IGRs, namely IGR J14466-3352 and J21565+5948.
IGR J14466-3352 2 (low significance) sources are detected (1/observation) Source #1 RA= 14h 46m 37.4s Dec. = -33d 52m 29.6s (±6 arcsec). The authors report a radio counterpart NVSS J144637-335234 but no optical nor infrared counterpart within the XRT error box. Source #2 RA = 14h 46m 31.1s Dec. = -33d 52m 37.6s (±6 arcsec ). No counterpart is found at any other wavelengths. The author slightly favour an association of the IGR with source #1, a putative blazar-type object. /P> IGR J21565+5948 Two sources are detected with XRT: Source #1 R.A. = 21h 56m 27.3s Dec. = +59d 47m 40.9s (±6 arcsec). A R~7 USNO-A2.0 object, also listed in the 2MASS survey (J, H, and K ~6.6) is found within the XRT error box. It is also a UVOT Bright Star Catalog (V and B ~7). The counterpart of this object is most likely the star CCDM J21565+5948AB, of spectral type AO. Source #2: is just at the border of the 99% IBIS error circle and is much more significant (~10 sigma). It is also a hard (> 3 keV) source. R.A.= 21h 56m 04.29s Dec. = +59d 56m 01.66s (±4.11 arcsec). It is coincident with an R ~16, B ~18 USNO-A2.0 object , and is also listed in the 2MASS catalogue (J ~16, H ~15 and K ~14). The source position is also compatible with 1RXS J215604.4+595607. The authors favour source #2 as the counterpart to the IGR. More details in Landi et al. 2010 ATel 3065 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#433 3 Dec. 2010 |
Romano et al. 2010
accepted in MNRAS, report the results of
Swift observations of IGR J18410-0535 and IGR J17544-2619.
They show that the former source displayed typical properties of SFXTs during its 2010-June outburst, in particular: - dynamical range of ~1600 in its flux variations - hard power law index, high energy cut off in its spectra - harder spectra for brighter states They estimate a B field < 3e12 G based on the constraint they get on the high energy cut-off. They also publish the results of their analysis of the 2010 March outburst of 17544-2619. The source displays properties typical of the SFXT class. It also showed a multi-peaked outburst. The authors suggest that these kind of events could be a defining characteristic of the class and is probably due to inhomogeneities in the companion's wind. More details in Romano et al. arXiV 1012.0028 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#432 01 Dec. 2010 |
Butters et al. 2010
accepted in A&A report RXTE and XMM observations
of intermediate polar candidates. Their sample includes 3 IGRs.
For each source they study the light curve and search for pulsations, and present
the spectral analysis of their observations.
>
The main results can be summarised as follows:
> IGR J00234+6141: A modulation is detected at the previously reported period of 563.5s. It seems to have an amplitude increasing with energy. The spectrum is hard and shows the presence of an iron line IGR J14536-5522: No coherent modulation at the previously identified period of 3.1 hr are seen, but the authors report the presence of a clear signal at periods likely to be harmonically related to it. The spectral fits are consistent with the source being a magnetic CV, with the presence of an iron line. The authors, however, mention a possible contamination by a nearby hard X-ray object. IGR J16167-4957: No significant peak is found in the periodogram of this source. The spectrum is fairly typical of that of an IP, and the authors conclude that this source is a good IP candidate More details in Butters et al. 2010 arXiV 1011.5762 Gotthelf et al. 2010 ATel 3057 report the discovery of 38.5 ms pulsar they name PSR J1849-0001. Based on its location and compatibility of its X-ray flux with that seen with XMM, they conclude to an association with IGR J18490-0000, therefore confirming the previously proposed pulsar/PWN nature of this source. Through their RXTE observation these authors can estimate barycentric P = 0.03851893151(31) s and P-dot ~1.40E-14 s/s at epoch MJD 55525.62. They derive the following pulsar parameters: spin-down power 9.6E36 erg/s, surface dipole magnetic field strength 7.4E11 G, and characteristic age 44 kyr. More details in Gotthelf et al. 2010 ATel 3057 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#431 23 Nov. 2010 |
Krimm et al. 2010 ATel 3051 report the observation
of a renewed hard X-ray activity of IGR J16318-4848 seen
with Swift/BAT.
The authors mention that this is the third large outburst seen with Swift since 2004. Earlier outbursts each lasted approximately 20 days. They also remark that the time between outburst is a multiple of the 80.2-day orbital period proposed for this source. Swift/BAT Hard X-ray Transient light curve for IGR J16318-4848: here More details in Krimm et al. 2010 Atel 3051 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#430 22 Nov. 2010 |
Chakraborty & Bhattacharyya 2010 2010 ATel 3044 report
RXTE of IGR J17480-2446, currently in outburst.
They observed significant cooling during decay of the bursts observed on 2010 November 13, 14, 15, 18. This might indicate the return of thermonuclear bursts as the persistent intensity but the authors also suggest other scenario for the apparent disappearance of the burst during the high intensity state of the source More details in Chakraborty & Bhattacharyya 2010 Atel 3044 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#429 18 Nov. 2010 |
Karino 2010 accepted in A&A present a study of constraints
of the orbital parameters of SFXTs on the model of clump accretion.
His/her main conclusion is that, based on typical parameters for the Sg star, systems of long orbital period cannot produce bright flare in the clumpy wind framework. In other word the clumpy wind scenario can well explain the burst seen in short period-moderate eccentricity systems. More details in Karino 2010 arXiV 1011.2812 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#428 09 Nov. 2010 |
Following the announcement of renewed activity from the candidate SFXT or Be X-ray binary IGR J19294+1816 (c.f. IGR circular #427, ATel:2983), Jenke et al. (2010, ATel:2985) report that pulsations have been detected for this source at high energy with Fermi-GBM. The barycenter-corrected pulse frequency is 80.3111(4) mHz for data corresponding to 27-29 October, 2010. Note that a similar pulse period of 12.4 s was discovered with RXTE (Strohmayer et al. 2010, ATel:2002). Please see Jenke et al. (2010): ATel 2985 The X-ray transient IGR J17285-2922 (= XTE J1728-295) has been making some headlines. First, Yang et al. (2010, ATel: 2991) analyzed a 2-ks Swift-XRT observation of IGR J17285-2922 during the decaying phase of its outburst (29 October, 2010). An absorbed power law model fits the data well with nH=6.2 (+1.4/-1.2) x 10^21 /cm2. This is consistent with the value obtained during the peak of the outburst when the luminosity was higher by an order of magnitude (c.f. ATel:2824). However, the photon index is 1.7(2) which suggests that the source spectrum hardens with decreasing intensity. Second, Russell et al. (2010, ATel:2997) monitored the position of IGR J17285-2922 in the I and R bands (mostly) with the Faulkes Telescope (N and S). They conclude that their "star 3" is the likely optical/IR counterpart of the X-ray source because of its variability (~0.4 in magnitude) and because of its blue (V-I) color compared with other candidate stars in the field (see also: ATel:2827, ATel:2870). Third, and lastly, Kong et al. (2010, ATel:3011) report the non-detection in the R-band of "star 3" during the quiescent phase of IGR J17285-2922 with the Pan-STARRS1 (PS1) 3Pi sky survey. This limits the magnitude in the R-band to > 21 during quiescence. All other optical counterpart candidates are detected in the R-band. Therefore, the authors conclude that "star 3" is the optical counterpart of IGR J17285-2922 given the variability between quiescence and outburst. Please see Yang et al. (2010), Russell et al. (2010), and Kong et al. (2010): ATel 2991, ATel 2997, ATel 3011. Pellizza et al. (2010) describe their analysis of optical/IR observations of IGR J16283-4838 with the ESO-NTT. Three candidate counterparts are located within the Swift error circle. The brightest of these (2MASS J16281083-4838560) is the most likely counterpart given its NIR-MIR SED that shows features (including luminosity, blackbody temperature, and absorption) typical of supergiant O or B stars. The distance to the source is estimated to be in the range of 13.6 to 21.6 kpc. The authors conclude that the source is a member of the highly-obscured HMXBs with supergiant companions. For more, please see Pellizza et al. (2010), accepted in A&A: arXiV 1011.1517 Finally, Lutovinov et al. (2010) discuss Swift, INTEGRAL, and BTA optical telescope observations of IGR J16547-1916. Thanks to Swift-XRT, the source position is refined to R.A. (J2000) = 16:54:43.7 and Dec. = -19:16:30 with an uncertainty of 3". The optical spectrum displays strong hydrogen and helium lines in emission, typical of the SED of a disk-accreting white dwarf, i.e. a cataclysmic variable system (CV). Coherent pulsations are seen in the optical light curve at a period of 549+/-15 s which they attribute to the spin of the white dwarf. The system is therefore an intermediate polar CV. The best-fitting spectral model to the X-ray data is a partially-absorbed bremsstrahlung at a temperature of ~21 keV, with nH~8 x 10^22 /cm2 and a covering fraction of ~0.94. The authors estimate the mass of the white dwarf to be 0.85(15) M_sol. Please see Lutovinov et al. (2010), accepted in AstL: arXiV 1011.1129 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#427 29 Oct. 2010 |
Pooley et al. (2010) analyzed a recent 10-ks Chandra ToO observation of IGR J17480-2446, the new transient LMXB pulsar in Terzan 5. They identify CXOGlb J174804.8-244648 (listed as CX25 in Heinke et al. 2003) which is located R.A. (J2000) = 17:48:04.831(4) and Dec.= -24:46:48.87(6) as the transient source currently in outburst. An image of the region can be seen in Pooley et al. 2010 (ATel:2974): ATel 2974 Bozzo et al. (2010) report the ISGRI detection of a new outburst from IGR J19294+1816, which is suspected of being either an SFXT or a Be X-ray binary (c.f. Rodriguez et al. 2009). The source is detected at the 30-sigma level in the 20-40 keV band of a 20-ks observation centered on GRS 1915-105 (13 ks of effective exposure on the IGR source). The observation took place on Oct. 28, 2010 between 18:25 and just after midnight (UTC). The spectrum can be fit with a blackbody at a temperature of 4.8(4) keV. The flux is 4.9(3)e-10 erg/cm^2/s in the 20-40 keV band. See Bozzo et al. 2010 ATel 2983 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#426 25 Oct. 2010 |
Pappito et al. (2010) provide a refined pulsation period and orbital solution for IGR J17480-2446, the new hard X-ray transient in Terzan 5. Based on 93 ks of RXTE data, they determine an orbital period of 21.2750(5) hr with a*sin(i)=2.4968(5) lt-s (reference epoch: MJD 55483.186). The pulsation period is measured at 90.539646(6) ms allowing them to constrain the magnetic field strength to between ~2x10^8 and ~2.4x10^10 G. These values place IGR J17480-2446 somewhere between the populations of "classical" (stronger magnetic fields, slower rotation) and millisecond (weaker magnetic fields, faster rotation) accretion-driven pulsars. The binary mass function is 0.021259(5) Msol in which the companion is a main-sequence star of 0.4--1 Msol. For more please see Papitto et al. 2010 (submitted to A&AL): arXiV 1010.4793 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#425 22 Oct. 2010 |
Fiocchi et al. (2010) describe the analysis of 10 Ms of ISGRI light curve
data dedicated to the suspected HMXB IGR J16328-4726. In most cases, the
source is not detectable (flux below 0.5 mCrab in the 20--50 keV range) in
single or collected science windows (ScWs) from public data gathered
between 29 January, 2003, and 20 March, 2009. The quiescent emission is less than 2.5 × 10^-12 erg/s/cm^2. Two strong outbursts are detected: one on 19 February, 2005 (53420.65 MJD), lasting about 1 hour; and the second on 28 January, 2009 (54859.99 MJD), lasting about 3.5 hours. In addition, there are several smaller outbursts (4-5 sigma) lasting several minutes to hours. Excepting different normalizations, all show similar spectral shapes in the ISGRI range. Using XRT data, they suggest 2MASSJ16323791-4723409 as the most likely candidate counterpart in the IR (see also Grupe et al. 2010: ATel 2075). With a dynamic range of over 170, combined with the sporadic emission behavior, and its known attributes, the authors conclude that IGR J16328-4726 is a new member of the class of SFXTs. Please see Fiocchi et al. 2010 (ApJL) for more: arXiV 1010.3529 In IGR J17480-2446, the recently-discovered X-ray transient pulsar in Terzan 5, the source is displaying a transition from Atoll to Z-like behavior with high-frequency QPOs (~48 Hz and ~173 Hz with rms amplitudes of ~2.7 and ~1.4, respectively, in the 2--60 keV range) and mHz QPOs (4.3+/-0.1 mHz with an rms amplitude of 1.5+/-0.8, in 2--60 keV) appearing mainly in the horizontal branch of the source's track in the hardness-intensity diagram. For more, please see Altamirano et al. 2010 (ATel:2952), and Linares et al. 2010 (ATel:2958): ATel 2952 and ATel 2958 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#424 15 Oct. 2010 |
Recent INTEGRAL observations of the field of the Terzan 5 globular cluster revealed an
X-ray transient (Bordas et al., 2010: ATel:2919) that was initially ascribed to
the LMXB called EXO 1745-248. Subsequent observations by Swift-XRT led to an improved X-ray position (Linares et al. , 2010: ATel: 2920) which is 5.3 arcsecs away from the Chandra position given for EXO 1745-248, and a soft X-ray spectrum (Bozzo et al., 2010: ATel:2922) that could be fit with an absorbed (nH = 0.50(8)e22 /cm2) blackbody of temperature 1.27(4) keV. JEM-X also detected the source undergoing a type-1 X-ray burst (Chenevez et al., 2010: ATel:2924). A pulsation frequency of 11.0452(2) Hz (corresponds to P = 0.090535(2) s) and an eclipse lasting 512(1) s were detected with RXTE (Strohmayer et al., 2010: ATel:2929). Moreover, burst oscillations were seen with RXTE at a period consistent with the neutron star's spin (Altamirano et al., 2010: ATel:2932). Heinke et al. (2010: ATel:2933) suggest that this transient is not the same source as the one seen in 2000 (EXO 1745-248) given that eclipses have never been observed in the latter source. Analysis of 150 ks of archival RXTE data revealed a strong QPO at a frequency of 690(23) Hz (Mukherjee et al., 2010: ATel:2935). The Swift position was further refined to RA (J2000) = 17 48 04.77 Dec. = -24 46 49.8 with a 90% error radius of 2.3 arcsecs (Kennea et al., 2010: ATel:2937). This is 6.8 arcsecs from the Chandra position of EXO 1745-248 thereby ruling out the association. An orbital solution was discovered with RXTE with parameters of 21.327(86) hr for the orbital period, a projected semi-major axis of asin(i) = 2.46(12) lt-s, and a T0 of 55481.783(7) MJD (Pappito et al., 2010: ATel:2939), which is consistent with the eclipse interpretation. Given that the association with EXO 1745-248 can be excluded, Ferrigno et al. (2010: ATel:2940) suggest that the source be renamed IGR J17480-2446. These authors also report the analysis of joint (as well as some simultaneous) RXTE and INTEGRAL data sets. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#423 27 Sept. 2010 |
Chakrabarti et al. 2010 ATel 2869 report the Chandra refinement
of the position to IGR J17285-2922/XTE J1728-295.
The source coordinates are: RA = 17h 28m 38.88s Dec= -29d 21' 43.6" (± 0.6 arcsec) therefore consistent with the Swift position. Further to that Torres et al. 2010 ATel 2870 report the results of optical observations of the field of this source. They measure a position of RA= 17h 28m 38.86s Dec= -29deg 21' 44.0" for the candidate optical counterpart previously suggested. This is still compatible with the Chandra position, but the authors also report at least two other point-like sources within the Chandra error box. The authors also confirm the lack of variability in this source More details in ATel 2869 and ATel 2870 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#422 23 Sept. 2010 |
Landi et al. 2010 ATel 2853
report Swift X-ray
follow up observations of the field of 3 IGRs.
The main results is the possible identification of an X-ray counterpart in each cases. IGR J09189-4418: RA = 09h 18m 58.65s Dec = -44d 18m 34.49s (±7.3 arcsec) This position contains 2MASX J09185877-4418302 that is classified as galaxy in NED which suggests an AGN nature. It also has an R~16.8 USNO-A2.0 counterpart. IGR J17233-2837: RA = 17h 23m 22.83s Dec = -28d 37m 51.65s (±4 arcsec). This coincides with 1RXS J172323.7-283805, and the X-ray position is compatible with USNO-B1.0 0613-0535226 an R ~19.5 object. IGR J18293-1213 RA= 18h 29m 20.01s Dec = -12d 12m 48.44s (5.3 arcsec). No catalogued optical and infrared counterpart is found within the XRT uncertainty. A bright object, however, lies just outside the XRT error box, and two other fainter objects are clearly seen in the DSS-II-red image inside the XRT uncertainty circle. More details in Landi et al. 2010 ATel 2853 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#421 21 Sept. 2010 |
Grebenev and Sunyaev Astr. Lett 2010, 36, 533
report the details of INTEGRAL observations of
IGR J18462-0223.
The source was detected in two different epochs, and accumulating these observations they obtain a position: R.A. = 18h 46m 16.6s Decl. = -02deg 23' 35" (+-1.6 arcmin). This position is compatible with the source being located in the Scutum-Centaurus arm of the Galaxy, that would indicate a distance of ~6kpc. The authors then present a spectral analysis of the source during the different outbursts. Although the spectrum of the 1st outburst may be slightly harder, they are both similar and can be well fitted with bremsstrahlung of temperatures ~40 keV, or power law with Gamma~2.5. The authors remark, however, that to be statistically acceptable the fit models need the addition of a cyclotron line at ~30 keV, even if they cannot completely conclude on the genuineness of its presence. Based on these results, the short duration of the outbursts, and the position of the source in the Galactic plane and possibly a Galactic arm, Grebenev and Sunyaev conclude that the source is a new member of the class of SFXT. More details in Grebenev and Sunayev; arXiV 1009.2454 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#420 14 Sept. 2010 |
In a study of LMXBs from the Galactic bulge, Zolotukhin and Revnivtsev 2010 accepted in MNRAS mention that they do not detect any source in the Chandra X-ray error of IGR J17505-2644 with J > 20.3 and H> 19.3. They however report a faint source with K=18.5 at this position. More details in Zolotukhin and Revnivtsev arXiV 1009.2454 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#419 10 Sept. 2010 |
Parisi et al. 2010 ATel 2839 report the results of
optical spectroscopy of the suggested X-ray
counterpart of IGR J20450+7530.
The optical spectrum of the source shows broad Halpha and Hbeta emission lines at z = 0.095 and a relatively flat continuum. No narrow emission lines are readily apparent. The authors conclude that the source is a Seyfert 1 AGN, and further confirm the association of the (Optical) X-ray and IGR sources. More details in Parisi et al. ATel 2839 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#418 9 Sept. 2010 |
Romano et al. 2010 accepted in MNRAS,
report results of their 2 year-long monitoring campaigns
of 3 SFXTs, namely IGR J16479-4514, J17544-2619 and
XTE J1739-302/IGR J17391-3021.
Thanks to their casual sampling of the X-ray light curves they can infer the duty cycles of each sources. Besides, they also obtain the spectral parameters of the sources during the 'out-of-outburs' phases, and show that the spectra are typical of neutron star XRBs, with rather hard photon indices (Gamma~1-2). They publish the complete list of BAT on-board detections of these sources, which indicates a continuous activity in those sources, and that true quiescence is a very rare state. Short term (~ks) variability is also observed and attributed to accretion of clumps from the donor star. Much more details can be found in Romano et al. arXiV 1009.1146 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#417 7 Sept. 2010 |
Landi et al. 2010 ATel 2830 report the results of
Swift follow up observations of IGR J20450+7530.
They find 3 X-ray sources at position compatible with that of the IGR. They study the properties of each of those sources and favour the source they label #2 as the counterpart to the IGR source as it is the only source detected above 3 keV. This object lies at RA = 20h 44m 34.47s Dec =+75d 31m 56.97s (± 4.69"). They report an R~16.6 and B~17.9 USNO-A2.0, and an J ~15.8, H ~14.7 2MAS X (2MASX J20443451+7531588), which is classified in NED as a galaxy, as the optical and IR counterparts. The X-ray spectra are well represented with a simple power law with Gamma ~1.7-2.0. The average spectrum requires an intrinsic absorption (Nh~0.2e22 cm-2) in excess to the Galactic one, and the photon index is then Gamma ~2.2? More details in Landi et al. ATel 2830 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#416 6 Sept. 2010 |
Russell et al. 2010 ATel 2827 report the results
of the search for optical counterpart to IGR J17285-2922.
They detect 3 faint sources within the 3.5 arcsec XRT error circle
(I-band), and a few more stars are visible near the edge of the
error circle.
Only 3 star are detected in the H-alpha image, and none show evidence for variability. Therefore the authors can not conclude further on the association of one of the star with the IGR More details in Russel et al. 2010 ATel 2827 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#415 2 Sept. 2010 |
Leyder et al. 2010 accepted in A&A, report INTEGRAL observations
of the field around Eta Car. In this field lies IGR J10447-6027
for which a refined position is given.
The new coordinates are RA = 10h44m36s, Dec= -60deg 25' 50" (±3 arcmin) More details (and the full analysis of Eta Car) can be found in Leyder et al. 2010 arXiV 1008.5366 Manousakis and Walter 2010 (accepted ?) report the results of their XMM monitoring of IGR J17252-3616, and re-analysis of INTEGRAL and RXTE data. They provide a refined orbital solution for the system: they obtain e>0.15, Porb=9.76 d, alphax sin i= 102 lt-s. Significant variations of Nh and the eq width of the iron line are also observed near the eclipse of the source. The variations of Nh are compatible with a model of a dense end extended hydrodynamical tail trailing the neutron star. In their simulation the latter structure is extends along most of the orbit, and the authors estimate a wind velocity vinf~400 km.s-1 They also conclude that most of the Fe emission is generated in the inner region of the tail, that does not contribute to the X-ray absorption. More details can be found in Manousakis et al. 2010 arXiV 1008.5362 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#414 1 Sept. 2010 |
Yang et al. 2010 ATel 2824 report the results of a Swift
follow up ToO on XTE J1728-295.
Only one bright source is found in the Swift XRT field of view at RA= 17h 28m 38.97s DEC= -29deg 21' 44.9" (± 3.5 arcsec ) therefore at a position compatible with that provided by RXTE. This position is not consistent with any of the 6 Chandra sources that had been previously found within the INTEGRAL error box for IGR J17285-2922 indicating that the source was in quiescence during the Chandra observation. The XRT spectrum is best fitted with an absorbed power-law model with NH =5.4 E21 cm-2 and Gamma= 2.23 similar to the photon index reported from previous INTEGRAL observations. Further to that Tuerler et al. 2010 ATel 2825 report that IGR J17285-2922 is detected by INTEGRAL with IBIS/ISGRI in the 20-40 keV band on several occasion. By combining more observations the source is even detected at 40-80 keV. The INTEGRAL position determined from these observation is consistent with that of Swift, which strengthens the association of the XTE and IGR sources. More detail in ATel 2824 and ATel 2825 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#413 31 August 2010 |
Markwardt et al. 2010 ATel 2823 report the detection of a new outburst
of a source dubbed XTE J1728-295, which is probably the same as IGR
J17285-2922.
The source is detected during PCA scans on 2010-08-28 when it rose to a 2-10 keV flux of 6.5 mCrab. The author estimate an upper limit of ~1 mCrab (@95%) during the previous 2 weeks. The position estimated from RXTE/PCA is consistent with IGR J17285-2922, and the authors conclude that IGRJ17285-2922 and the XTE source are very likely to be the same source. More details can be found in Markwardt et al. ATel 2823 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#412 30 August 2010 |
Kuulkers et al. 2010 ATel 2820 report the observation of flaring activity from the SFXT IGR J17544-2619 with IBIS/ISGRI. The source is also detected with JEM-X over the observation. More details in Kuulkers et al. 2010 ATel 2820 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#411 24 August 2010 |
Pavan et al. 2010 ATel 2809 report the discovery
of a new INTEGRAL source, IGR J16374-5043, with IBIS/ISGRI.
The source is detected at 20-40 keV (resp 40-80 keV) with a flux of 10 mCrab (resp. 9 mCrab). The source coordinates are RA = 16h 37m 22s DEC= -50° 43' 48" (± 2 arcmin) Investigation of the light curve revealed the presence of a bright flare on 2010 August 22 at 00:40, lasting for about 0.9 days. The peak of the flare is reached approximatively two hours after the onset of the burst. Further to that Bozzo et al. 2010 ATel 2810 report the results of Swift follow up observations of the source field. They detect a faint X-ray source within the IBIS error box at a position RA= 16h 37m 13.5s, DEC= -50° 43' 29.3" (± 4.7 arcsec) The authors further discuss their results and conclude that the faintness of the source is compatible with the rapid fading seen with INTEGRAL. More details, including the results of basic spectra fittings can be found in ATel 2809 and ATel 2810 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#410 20 August 2010 |
Townsend et al. 2010 present X-ray and optical/IR analyses of the Be-XRB IGR J01054-7253 in the SMC.
From optical/IR observations, the orbital period of the system was determined to be 36.70(3) days.
These observations allowed the spectral class to be constrained to O9.5-B0, in agreement with Masetti et al. (2010),
but with a with a later luminosity class of IV-V rather than III as previously proposed. The distance to the source is estimated to be 71(5) kpc. Analysis of RXTE/PCA data shows an orbital modulation in X-rays as well with a period of 36.3(4) days, consistent with the optical/IR results, a semi-major axis of 167(7) lt-s, and eccentricity of 0.28(3). The spin period was determined to be 11.48143(1) s with a spin-up rate of -4.67(31)e-10 s/s, thereby satisfying the theoretical relation between luminosity, spin period, and spin-period derivative in accreting X-ray binaries. An absorbed cutoff power law fit to the combined spectra from RXTE and XMM-Newton yield nH=2.3(6)e21 /cm2, Gamma=1.06(5), Ecut=9(-1+2) keV, and Efold=22(4) keV. For more information, please see Townsend et al. (2010) accepted for MNRAS: arXiV 1008.3361 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#409 6 August 2010 |
Tazaki et al. 2010 describe their analysis of an 80-ks Suzaku observation of IGR J21247+5058 (= 4C 50.55).
This object is the brightest broad-line radio galaxy in the hard X-ray sky (> 10 keV). The broadband (1--60 keV) spectrum combing Suzaku and Swift data can be represented by a power law (gamma = 1.65(4)) featuring a high-energy cutoff (~ 105 keV), dual absorption layers (nH1 ~ 7.9x10^22 and nH2 ~ 0.75(3)x10^22 with a covering fraction of f = 21(3)%), and a reflection component (solid angle: Omega/2pi = 0.2) from cold matter in the disk. According to the SED, the jets contribute a negligible amount to the total X-ray emission. A thermal comptonization model fit to the spectrum reveals a cold (kT ~ 31 keV) and optically-thick corona (tau ~ 3). The narrow Fe-Kalpha emission line (EW ~ 19 eV) suggests a disk that is truncated and/or whose `inner radii are shielded by a comptonizing medium that dampens relativistic broad-line features. The authors discuss these results as they relate to the disk structure around accreting black holes with strong jets. For more information, please see Tazaki et al. 2010: arXiV 1008.0722 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#408 2 August 2010 |
Chenevez et al. 2010 accepted in MNRAS present an extensive investigation
of the burst properties of IGR J17473-2721 during its 2008 outburst.
Using different instruments (RXTE, Swift, INTEGRAL, Agile) these authors
detect a total of 57 thermonuclear bursts, whose (spectral and temporal) properties
are given.
The authors then study the bursting behaviour and burst properties of this source and remark several things. -The burst rate first increases with the accretion rate until it stops. It resumes at a much lower accretion rate. The authors discuss the possible origin of this hysteresis, and favours the occurrence of a (missed) super burst as the origin of the quenching of bursting activity. -Some of the bursts are identified as photospheric radius expansion bursts, and these are used to estimate a distance to the source of 5.5±0.8 kpc -They distinguish 7 phase of burst behaviour, which are attributed to 4 burst regimes: Mixed H/He flashes, pure He flashes (with stable H burning), rich He flashes at low dot(m) and no burst ie stable H and He burning. Much more details, including discussion of all these behaviours in the context of bursters, can be found in Chenevez et al. 2010 arXiV 1007.5201 Corbet et al. 2010 ATel 2766 report the discovery of the pulse period of the sgHMXB IGR J16493-4348 in RXTE data. Analysing a 8ks RXTE observation of the source, these authors found a highly significant modulation at 1069±7 s. The amplitude of the modulation is about 20%. Corbet et al. add that the value of this pulse period is consistent with the range of periods seen in other sgHMXBs More details in Corbet et al. 2010 ATel 2766 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#407 27 July 2010 |
Lutovinov et al. 2010
ATel 2759 report the identification of
IGR J03249+4041 as a pair of interacting Seyfert 2 galaxies.
The authors first remark that the field of this source has been observed
with Swift/XRT, and that the INTEGRAL error box of the IGR contains
a faint possibly extended source. Further analysis shows that this
source probably consists of two point sources respectively located at:
Source A: RA=03h25m13.2s Dec=40deg41m51s Source B RA=03h25m12.4s Dec=40deg42m01s The latter being the hardest and brightest of the two. These 2 sources can be identified with the core of interacting galaxies LEDA 97012 and 2MASX J03251221+4042021. Lutovinov and collaborators performed spectroscopic observations of these sources and conclude that both objects are Sey 2 AGN located at z=0.047521 (source A) and z=0.04759 (source B). The authors further discuss the associations of the IGR with other objects in this field and conclude that IGR J03249+4041 is also consistent with being SWIFT J0324.9+4044 and PBC J0325.1+4042, and the soft X-ray source RX J0325.2+4042. All these high energy objects being the counterparts to the pair of interacting Sey 2 galaxies LEDA 97012 and 2MASX J03251221+4042021 More details in Lutovinov et al. 2010 ATel 2759 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#406 26 July 2010 |
Drave et al. 2010 accepted in MNRAS report the discovery of
a 51.47 d period in analysis of 12.4Ms of INTEGRAL data of the SFXT
XTE J1739-302/IGR J17391-3021.
This period is interpreted as the orbital period of the system. They further report the observation of 35 epochs of outburst throughout the orbit. From the variable duration and orbital location of the outbursts the author exclude that the source is powered by Roche lobe overflow. The long period allows them to estimate the semi major axis to be within 173.4-179.8 Rsun, which permits eccentricities up to 0.8. The authors further discuss their findings, and add that the neutron star probably orbits in an inhomogeneous clumpy wind, and conclude that there may be some enhanced equatorial density region in this system. More details in Drave et al. 2010 arXiV 1007.3379 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#405 20 July 2010 |
Altamirano et al. 2010 report the discovery of burst oscillations
at the spin frequency in the ms pulsar IGR J17511-3057
mainly from RXTE observations.
The authors perform a fine spectral and temporal analysis of
data showing type I burst. They remark that in this source the
properties of the burst oscillations are similar to those of other
persistent accreting ms pulsar, even though the oscillations are
not detected during the whole duration of the bursts.
They present a detailed analysis of the burst properties in this source and discuss their finding in this context. Much more details in Altamirano et al. 2010 arXiV 1005.5299 Ratti et al. accepted in MNRAS report on Chandra and optical/NIR follow up observations of 11 X-ray sources, 8 of which are IGRs. For all but one they provide the refined Chandra position and present the analysis of optical/NIR observations that allows them to classify the source. For the last, only the XMM Newton position is given, and the authors are therefore unable to identify the true counterpart. All details, positions, counterparts, and discussions on the type of these sources can be found in Ratti et al. 2010 arXiV 1007.2495 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#404 13 July 2010 |
Landi et al. 2010
ATel 2731 report the results of
Swift observations of the field of 2 IGRs from the 4th
IBIS Catalogue.
IGR J05255-0711: 3 possible X-ray counterparts are found within
the IBIS 99% error box.
Amongst the 3 only one source is detected at more than 3 sigma:
it lies at RA=05h 25m 09.83s Dec = -07d 07m 48.38s (+- 4.6 arcsec). It is also the only of the 3 that is visible at E > 3 keV.This object is compatible with the radio source NVSS J052509-070746 (20 cm flux of 177.22 mJy), and an USNO-A2.0 source with magnitude R ~ 18.9. The X-ray spectroscopy indicates a steep power law spectrum (Gamma ~2.2). The authors favour this source as the counterpart to the IGR. br> The NVSS finding chart can be found here IGR J16413-4046: A faint 2.5 sigma source which disappears at soft energies (0.3-3 keV) is found within the IBIS error box. it is located at RA = 16h 41m 19.31s Dec = -40d 47m 31.84s (+-7.7 arcsec). This position is compatible with a USNO-A2.0 object with R ~15.6, which is also an IR object (2MASS) with I ~13.65, H ~13.23 and K ~13.27. More details in Landi et al. 2010 ATel 2731 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#403 8 July 2010 |
Sidoli et al. 2010 accepted in MNRAS
report the results of their Suzaku observations
of IGR J08408-4503 dring a long low intensity state.
They separate the observation in 3 different periods, based on the source behaviour. The first is the low intensity state itself that is well represented by a thermal emission probably arising from the companion and a power law both undergoing Galactic absorption. The next 2 states correspond to flares, and are well represented by locally absorbed powerlaw (in addition to the thermal plasma). The spectral parameters of the 2 flares are consistent. They then compare their observations to a previous XMM caught in a similar state and conclude that the Suzaku models can adequately represent the XMM spectra. They conclude by saying that even at very low luminosity the source still accretes matter. More details including calculations about clump mass and density can be found in Sidoli et al. 2010 arXiV 1007.1091 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#402 30 June 2010 |
Reig et al. 2010 accepted in A&A report the results of long term
optical monitoring of IGR J06074+2205. The authors study
both the photometry and spectroscopy of the system.
They first refute the previously proposed spectral classification of the star and classify it as a B0.5 Ve star, while they also mention that a B1 Ve cannot be completely excluded. They determine a distance of 4.5 kpc that should be taken as a lower limit. The observation of a profile change of the Halpha line indicates changes in the structure of the disc with a complete disappearance of the latter. Reig et al. 2010 further discuss their findings and compare them with other known Be objects. More details, including discussion about density perturbation in the disc, can be found in Reig et al. arXiV 1006.4935 Rau et al. 2010 ATel 2704 report the results of Swift/UVOT and GROND observations of the new transient IGR J05414-6858. They found that the 2MASS counterpart previously suggested is, in fact, a blended object. Only one source is, however, seen in the UVOT detector. It lies at RA(J2000) = 05:41:26.66, Dec(J2000) = -69:01:23.7 and has magnitudes g = 15.53, r = 15.75, i = 16.11 +/- 0.05, z = 16.17, J = 16.3, H = 16.8 , K = 17.3, V = 15.37, B = 15.19, U = 15.05, UVW1 = 15.05, UVM2 = 15.10, UVW2 = 15.03. The SED of this source is best represented by a B1-2III stellar template. The authors further conclude that this source is the optical/NIR counterpart of IGR J05414-6858, and they classify it as a transient Be-HMXB in the LMC. More details in Rau et al. 2010 ATel 2704 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#401 28 June 2010 |
Grebenev & Lutovinov 2010 ATel 2695 report the discovery of a new
source IGR J05414-6858 located at R.A.=05h41m26s, Decl.=-68d58m23s (uncertainty 2.5'). The source is dubbed transient, and its luminosity at the distance of the LMC is 8 E36 erg/s. Further to that Lutovinov & Grebenev 2010 ATel 2696, report the results of a Swift observation of the field of the new source. They found a faint X-ray object at RA=05h41m26.7s, Dec=-69g01m25s (uncertainty of ~3") which is ~ 3' away from the IBIS position of the IGR. The source spectrum is powerlaw like, with Gamma=0.33 and a flux consistent with the INTEGRAL one. They identify 2MASS 05412663-6901224 (J=15.084, H=14.853, K=14.989) as a possible counterpart to the source. It is also an USNO-B1source (0209-0129816), with R=15.6. More details in Grebenev & Lutovinov Atel 2695 and Lutovinov & Grebenev ATel 2696 I also bring your attention to the publication of the last IBIS 7-year all sky survey by Krivonos and co-workers. The paper comes in 2 parts, the first detailing the methods of image reconstruction, while the second is the catalogue of source itself. More details In Krivonos et al. 2010 arXiV 1006.2463 and arXiV 1006.4437. On the source identification side, Masetti et al. 2010 accepted in A&A, report the results of optical spectroscopy and hence identification of 44 source 33 of which have an IGR name. Beside giving the type of each of the source, the authors also discuss the repartition of sources in terms of family, and give some statistics of the sources identified through optical and/or IR spectroscopy. More details in Masetti et al. 2010 arXiV 1006.4513 Finally Fiocchi et al. 2010 accepted in ApJ report the results of Chandra observations of the field of 5 IGRs namely IGR J10447-6027, IGR J16377-6423, IGR J14193-6048, IGR J12562+2554, and IGR J12288+0052. The first is associated with an IR source, the second is associated to a cluster of Galaxy, the 3rd with a PWN and the 4th with a quasar. The association of the last source is less secure although it is suggested to be an AGN. More details in Fiocchi et al. arXiV 1006.4462 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#400 21 June 2010 |
Ducci et al. (2010)
accepted in MNRAS report the results of
observations of several SFXTs and the theoretical interpretations
of their behaviour.
They studied the INTEGRAL archival data base of 14
sources 10 of wich are IGRs. They report the observations
of several new outbursts for each sources.
They then turn to the sources that show the highest numbers of outburst, IGR J16479-4514, to which they apply their clumpy wind accretion model. Based on this model they obtain parameters for the wind of the secondary in this system. Since they obtain at least two parameters that differ from wht observed in other systems, they study other possible additional mechanisms that could explain the source behaviour. They conclude that the X-ray photoionization in this particular source, in XTE J1739-302 (IGR J17391-3021), IGR J17544-2619, and in general systems with short orbital periods could lead to the formation of a transient accretion disc, the accretion of which could be responsible for (part of) the flaring activity. In longer period sources the latter effect can be neglected. More details, including a discussion of the Rayleigh-Taylor instability as the origin of certain types of flares are also presented in Ducci et al. 2010, arXiV 1006.3256 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#399 11 June 2010 |
Bodaghee et al. (2010) report on our analysis of an
~80ks Suzaku observation of IGR J16207-5129.
The broadband (0.5--60 keV) spectrum contains unprecedented sensitivity above 15 keV which allows us to constrain the cutoff energy for the first time: 19(-4/+8) keV. The location of the cutoff argues in favor of a neutron star as the compact object. The source spectrum is strongly absorbed with nH=16.2(-1.1/+0.9)x10^22 /cm2 which is well above the expected interstellar value indicating that there is a substantial amount of material in the vicinity of the X-ray emitter. Intriguingly, the observation concludes with a ~30 ks epoch in which the source flux is close is extremely low for a sustained period (and no accompanying change in the nH or gamma). Several mechanisms are explored to explain the diminished flux, with one viable scenario being that the X-ray source is partially or fully eclipsed by its supergiant companion. The putative eclipse requires further observations in order to be confirmed. Assuming the eclipse is real, we employ a model for eclipsing HMXBs which help us constrain some of the orbital parameters such as the orbital period (4d <= P <= 9 d) and inclination angle (i >= 50 degs). For more information, please see Bodaghee et al. (2010) accepted in ApJ arXiV 1006.1911 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#398 11 June 2010 |
Malizia et al. (2010) report their analysis
of archival XMM data of 6 newly-discovered gamma-ray
sources (4 of which are IGRs) from the 4th ISGRI catalog of
Bird et al. (2010). Astrometric and spectroscopic results for
each source are summarized below:
IGR J15359-5750: (R.A.;Dec.;error radius) = 15:36:02.99; -57:48:52.2; 3.2" 0.2--12 keV flux: 0.137(4) cps likely counterpart(s): 2MASS 15360282-5748529, MGPS J153602-574854 nH=20.1(+2.5/-2.9)x10^22 /cm2 with a partial covering fraction of 0.95(+0.02/-0.04) Gamma=1.85(+0.27/-0.25) possible classification: AGN of intermediate type IGR J17331-2406: No source detected in the IBIS error circle. possible classification: Galactic X-ray transient IGR J17445-2747: (R.A.;Dec.;error radius) = 17:44:29.41; -27:46:08.9; 5.1" 0.2--12 keV flux: 0.520(184) cps likely counterpart(s): 2MASS 17442946-2746114 possible classification: Galactic X-ray transient IGR J18538-0102: (R.A.;Dec.;error radius) = 18:53:48.46; -01:02:29.7; 3.2" 0.2--12 keV flux: 0.262(8) cps likely counterpart(s): 2MASS 18534847-0102295, 1RXH J185348.2-010228 nH=0.4(1)x10^22 /cm2 Gamma=1.56(8) possible classification: background AGN Further information on these sources (as well as for 2 ASCA HMXBs) can be found in Malizia et al. (2010) accepted in MNRAS arXiV 1006.1272 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#397 11 June 2010 |
Papitto et al. (2010) accepted in MNRAS report an in-depth XMM and
RXTE analysis of the accreting ms pulsar (AMP) IGR J17511-3057.
They observe pulsations at 244.8339512 Hz that are present all along the outburst, with a pulse fraction of 14.4%. They derive an orbital period of ~3.5 hours. They report the detection of 2 type I X-ray bursts, that they attribute to a pure helium environment. No photospheric radius expansion is observed and the authors give a lower limit to the distance of about 6.5 kpc, which indicates that the source probably belongs to the Galactic bulge. XMM and XMM+RXTE spectral analysis are presented, and the authors conclude to the presence of several emission processes in the spectra: thermal components due to an accretion disc, and of the neutron star surface, thermal comptonisation, reflection on the accretion disc (skewed iron line, and compton hump). All spectral parameters, a deeper analysis of the pulse energetic dependence and a discussion of this source in the context of AMPs can be found in Papitto et al. arXiV 1005.4827 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#396 09 June 2010 |
Clark et al. (2010) (accepted?) in MNRAS report the discovery of
a 30.32d orbital period in the SFXT IGR J16465-4507 from long term
IBIS and BAT light curves. They also find a total of 11 periods of outbursts, 9 of which had never been published before. The authors present the spectral analysis of periods of outburst and discuss the spectral parameters in the context of outbursts of SFXTs. Based on the type of the companion, they estimate a semi-major axis of the orbit of 121.9-126.3 R_sun, with eccentricities either <0.6 or <0.8 depending on the exact mass of the donor. The authors finally confirm that this object can be considered as an intermediate SFXTs given its smaller dynamical range compared to other systems. More details in Clark et al. 2010 arXiV 1005.4763 De Pasquale et al. 2010 ATel 2661, report the detection of yet another outburst of IGR J18410-0535 seen with Swift. The authors report a basic Swift spectral analysis of the event, and mention the non-detection of the source with UVOT with the white filter. A more thorough analysis of the same event is reported in Romano et al. 2010 ATel 2662. Please see De Pasquale et al. 2010 ATel 2661 and Romano et al. 2010 ATel 2662 for all details about this event. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#395 10 May 2010 |
Schmidtke et al. (2010) describe the MACHO light curve of the optical counterpart to the probable Be X-ray binary IGR J05007-7047. The long-term light curve shows recurrent dips in stellar magnitude (0.1-0.5 mag) every 600-800 days. A periodicity of ~28 days is revealed in the light curve which is consistent with the recently-identified X-ray period of 30.77 days (ATel #2594, #2597) and which is suspected of being the binary orbital period. Please see Schmidtke et al. (2010) for more information: ATel 2601 The accreting millisecond X-ray pulsar (AMXP) IGR J00291+5934 underwent a double-peaked outburst in 2008 that lasted ~100 days. The multi-wavelength analysis (from radio to X-rays, including the most detailed IR-UV SED of an AMXP) of this outburst is reviewed in Lewis et al. (2010). The authors find that the first peak (Aug. 2008) exhibits a rapid decline, whereas the second peak (Sep., 2008), which has a shape that is similar to the 2004 outburst (at least in optical), features a plateau phase lasting ~10 days that is also present in the X-rays. Periodicities are not seen in the light curve even at the established orbital period of 2.46 hours. The optical spectrum contains a blue component plus a double-peaked H-alpha profile typical of an irradiated accretion disk, but not the other lines that were visible in the 2004 outburst. There is also a transient NIR excess consistent with an optically-thin synchrotron jet. The authors discuss the morphology of the double-peaked outburst in relation to the more common single-peaked outbursts. Their study has implications for the active duty cycle of X-ray transients with short periods, as well as for disk-jet coupling in accreting neutron stars. More information can be found in Lewis et al. (2010), accepted in A&A: arXiV 1005.1178 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#394 6 May 2010 |
La Parola et al. 2010 and Cusumano et al. 2010 both accepted in MNRAS report the identification of the orbital period of, respectively, IGR J16465-4507 and J16493-4348, from the Swift/BAT light curves. IGR J16465-4507: A significant periodicity is found at P=30.243 d. La Parola et al. also report the observation of a wide phase of 0 intensity at T(MJD)=54180.5+- nPorb. These results allow them to estimate a semi-major orbital axis a~125 Rsun (150 Rsun)~6 Rstar (5 Rstar) for a typical 09.5 I (B0.5 Ib) star. They further discuss their findings and do not favour an eclipse as the origin of the minimum phase. La Parola et al. add that the lower flux of this source, compared to typical sgHMXB, could be due to the larger separation between the 2 components. IGR J16493-4348: A significant periodicity is found at 6.782 d. Cusumano et al. also report the identification of an eclipse in the folded light curve at T(MJD)=54175.92 +- n*P These results allow them to estimate a semi-major orbital axis a~55 Rsun~2 Rstar with a maximum eccentricity 0.15. More details can be found in La Parola et al. arXiV 1005.0684 and Cusumano et al. arXiV 1005.0709 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#393 5 May 2010 |
D'ai et al. 2010 ATel 2596 identify a strong modulation
at 8.452d in the 15-50 keV BAT light curve of IGR J17354-3255 which
is attributed to the orbital period of the system.
They remark that the folded light curve is structured and they
infer an eclipse at date 52726.25 ± n P_orb.
A spectral analysis of the total spectrum is also provided
More details in D'ai et al.
ATel 2596
Coe et al. 2010 ATel 2597 confirm the optical
counterpart and period of IGR J05007-7047
through an identification of LMC130.4 19472
as the optical counterpart.
They found a period of 30.80 d in the 8 years I-band
light curve of this system.
More details in Coe et al.
ATel 2597
Corbet et al. 2010 ATels 2598 and 2599 report
the discovery of periods in IGR J14488-5942/Swift J1448.4-5945
and IGR J16493-4348 from Swift/BAT and RXTE (for the latter
source).
IGR J14488-5942: The power spectrum extracted from the 15-100 keV
light curve of this source reveals a significant modulation at 49d.
A sine wave fit to the light curve leads to the following ephemeris:
Tmax = MJD 54 318.1 + n x 49.51
where Tmax is the time of maximum flux.
The authors also discuss their search for a spin period in the 2
possible counterparts found with XRT, and while they see a marginal
signal at 33.4s in one of the source they do not favour this object as
the counterpart to the IGR. Corbet et al. also interpret the pulsation
as the orbital period of an HMXB possibly a Be type.
IGR J16493-4348: A highly significant pulsation is seen in the power
spectra extracted from both the RXTE/PCA 2-10 keV Swift/BAT
light curves at a period ~6.8d.
A sine wave fit to the light curve leads to the following ephemeris:
Tmax (BAT) = MJD 54 301.39 + n x 6.7906
Tmax (PCA) = MJD 54,301.55 + n x 6.7851
where Tmax is the time of maximum flux.
This period is typical of an orbital period for an HMXB with a Sg companion.
Corbet et al. also report the identification of a significant second pulse in both lcs at around 20.07-20.09 d, which differs from an harmonic of the first pulsation. They discuss its possible nature (other XRB in the field, superorbital modulation,..) More details in Corbet et al. 2010a,b, ATel 2598, ATel 2599 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#392 4 May 2010 |
La Parola et al. 2010 ATel 2594 report the discovery
of a 30.77d period in IGR J05007-7047 from the 15-50 keV
Swift/BAT long term light-curve.
The light curve folded at this period shows a sinusoidal shape with a
dip that they authors find consistent with the occultation of the
source by the companion star.
The period is thus interpreted as an orbital period.
The authors also include the results of a spectral analysis of the long term Swift spectrum. More details in La Parola et al. 2010 ATel 2594 Telezhinsky et al. 2010 accepted in A&A publish a catalog of variable sources detected by INTEGRAL. Among all sources detected by INTEGRAL they find than 202 sources are variable according to their definition (well described in the paper) on time scales > the duration of a science window. A significant number of these sources are IGRs. Much more details, including histograms of the number of variable source per type of objects, or vs the degree of variability can be found in Telezhinsky et al. 2010 arXiV 1005.0249 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#391 29 April 2010 |
Corbet et al. 2010 ATel 2588 report the detection of
a ~10 day period in IGR J16328-4726 while analysing the
long term Swift/BAT (15-100 keV) light curve of the source.
The source mean flux is about 1.3 mCrab and the light curve
is fitted with a sine wave with the following characteristics Tmax (MJD) = 54,256.08 + n x 10.076 where Tmax is the time of maximum flux, with a 100% flux modulation. They do not detect pulsation at shorter period when lookin at an XRT light curve with 5s resolution. The authors interpret the 10 d period as being an orbital period, which is suggestive of an HMXB. Corbet et al. add that the fact the source is intrinsically absorbed is consistent with an HMXB powered by wind accretion More details in Corbet et al. 2010 ATel 2588 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#390 27 April 2010 |
Nespoli et al. 2010 accepted in A&A
publish the details of their
IR observations and analysis of the counterpart to IGR J16493-4348.
They present the observations that led them (ATel 1396) to classify the source as a B0.5-1 Ia-Ib object, making the IGR a supergiant HMXB. In particular the IR spectrum presents stron He I emission (at 20581 Angstrom) strong He I absorption (21126A) and strong Br_gamma (21661A) in absorption that are typical of this type of object. They also estimate the absorption on the line of sight to be Nh~2.9 10^22 cm-2 which is compatible with the tabulated value in this direction of the Galaxy, but still an order of magnitude lower than the value obtained through X-ray spectral fits. They conclude that the excess absorbing matter is local to the X-ray source. They also gie a range of distance to the source between 6 and 26 kpc. More details can be found in Nespoli et al. 2010 arXiV 1004.4101 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#389 19 April 2010 |
Corbet et al. 2010 ATel 2570
report the results of
Swift/BAT and RXTE/PCA monitoring of the pulsar
IGR J16393-4643.
They did not find any of the previously reported period in
the long term light curves from the two instruments.
They, however, discovered a highly significant modulation
at 4.2 days in both light curves.
From fits with sine wave to the LCs they derive Tmax (BAT) = MJD 54,352.50 (+/- 0.09) + n x 4.2368 (+/- 0.0007) Tmax (PCA) = MJD 54,352.39 (+/- 0.11) + n x 4.2371 (+/- 0.0007) For both light curves, the semi-amplitude of the modulation divided by the mean flux is approximately 25%. Corbet and collaborators discuss their finding and interpret this modulation as likely being the orbital period of the system. With this period the source still lies in the Sg-HMXB region of the Corbet diagram, and the authors therefore conclude that IGR J16393-4643 is very probably such a system, and not a symbiotic system. More details can be found in Corbet et al. ATel 2570 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#388 16 April 2010 |
Bozzo et al. 2010 accepted in A&A
report XMM analysis
of 2 SFXTs, IGR J08408-4503 and XTE J1739-302 (aka
IGR J17391-3020) during quiescence.
They first observe that the quiescent emission is composed
of multiple flares occuring after period of faint X-ray emission.
In both sources the hardness ratio and the intensity are positively correlated.
The spectral analysis of the two sources, shows the presence of a soft component below 2 keV, in addition to a standard (cutoff) power law with absorption. This excess is well represented by either a black body or thermal plasma model. Bozzo et al. discuss their finding, and in particular suggest that the soft component, if indeed due to a thermal plasma, could be the X-ray emission due to shocks in the wind of the supergiant companion. Much more details (including a discussion of the spectral properties of the source wrt different models proposed for the mechanisms at work in SFXTs) are given in Bozzo et al. 2010 arXiV 1004.2059 Coe et al. 2010 accepted in MNRAS report the results of an INTEGRAL monitoring campaign of the SMC. These observations have allowed these authors to discover 1 new source, and 2 candidates new sources IGR J00515-7328 was detected in Rev 812 and then marginally in the next three satellite revolutions. The overal significance is 5.9 sigma. A Swift/XRT pointing showed an X-ray source compatible with being the IGR at RA=00h 51m 59s Dec=-73deg 29' 25" (±5.2") This position is compatible with a Rosat PSPC source. The authors also remark the presence of several XMM sources in the IBIS error box. The author seem to favour the association of the Swift/XRT source with the IGR although they clearly mention that they cannot be unambiguously associated. A hint for a pulsation at 8.29s is alsor reported but it cannot clearly be associated to the IGR. Possible IR counterparts are also found at positions consistent with the XRT-Rosat source both compatible with being Be stars. An HMXB type is suggested for this source IGR J00523-7217 is found at 5.3 sigma at RA=00h 52m 19s Dec=-72deg 17' 06" (±4.7 arcmin). This potential source is spatially coincident with 2 Be stars IGR J01134-7325 was found with JEM X with a significance of 3.3 sigma at: RA= 01h 13m 06s Dec=-73deg 25' 17" (±1.8 arcmin) More details in Coe et al. 2010 arXiV 1004.2219 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#387 15 April 2010 |
Fiocchi et al. 2010 ATel 2562 report the results of
a Swift observation of IGR J14549-6459.
A single X-ray source is found with the XRT at RA= 14h 55m 23.9s, Dec= -65d 00m 03.2s (±6") Two USNO-B1.0 sources with R magnitudes in the range 16.13-16.67 and 16.90-16.97 respectively are found within the X-ray position. The first of the two sources also has a counterpart in the 2MASS survey catalogue with J, H and K magnitudes of 14.98, 13.82 and 12.80. The X-ray spectrum is well fitted with an absorbed power law with an intrinsic absorption NH = 1.38 e22 cm-2 and Gamma = 1.8 (fixed). Landi et al. 2010 ATel 2563 add to the recent identification of IGR J13550-7218 with an XRT source, the identification of the source from previous multi-wavelengths catalogues. SUMSS J135512.53-721916.2 ( 36 cm flux of 18.8 mJy) most likely associated to PMN J1355-7219, which could suggest that the source has a flat radio spectrum. They also report the presence of 2MASX J13551345-7219150, coincident with the USNO-B1.0 object previously reported and associated with to the galaxy WKK2657. Landi et al. conclude confirming the AGN nature of this source More details in Fiocchi et al. 2010 ATel 2562 and Landi et al. 2010 ATel 2563 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#386 14 April 2010 |
Rodriguez et al. 2010
ATel 2557 report the results
of Swift observations of 2 new IGR sources from the last
IBIS catalogue, namely IGR J13045-5630 and J13550-7218.
IGR J13045-5630: We found a 3.9 sigma source in the X-ray at R.A.=13h 04m 31.5s Dec.=-56deg 30' 54.8" (+- 6.6" at 90% confidence) A single m(UVW2)=19.1 UVOT source lies within the X-ray error box. While we did not find any counterpart in the SIMBAD, 2MASS, 2MASX, and NED catalogues, we, however, found 3 sources USNO B1.0 catalogue. The closest in position to the UVOT source (1.2" offset) is USNO B1.0 0334-0372825, that has m_I=12.6 m_R=13.0 m_B=14.4. Given the faintness of the source we could not perform a meaningful spectral analysis. IGR J13550-7218: We found a 4.4 sigma source at R.A.=13h 55m 13.05s and Dec.=-72deg 19' 11.62" (+-5.7" at 90% confidence). A single m(UVW2)=20.0 UVOT source lies within the XRT error box. We only found a counterpart in the USNO B1.0 catalog which is also compatible with being the optical counterpart to the UVOT source. USNO B1.0 0176-0353892 has m_I=15.6 m_R=15.1 m_B=16.8. The XRT spectrum seems well represented by an absorbed power law although the parameters are very poorly constrained. We obtained N_H=19 -9 +8 10^22 cm-2, with Gamma pegging at the highest value allowed (3). Our results lead us to suggest that this source could possibly be an AGN. More details in Rodriguez et al. 2010 ATel 2557 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#385 13 April 2010 |
Renaud et al. 2010 accepted in ApJ report the results of
multi-wavelength observations of the field containing IGR J14003-6326.
The authors provide timing and spectral analysis of the radio, RXTE, Chandra, and INTEGRAL data. Using RXTE data the authors discovered a pulsation at 31.18 ms which allows to classify the source as a ms pulsar. The pulsar is most likely associated to a point source seen with Chandra at the centre of a G310.6-1.6 that the authors classify as a PWN. The source is detected in the radio band as well as its pulsed emission, while it is not detected by Fermi. From analysis of all these facilities, Renaud et al. estimate a spin down luminosity of 5.1e37 erg/s which implies a surface magnetic field of 1.1e12 G. They further conclude that the source lies at about 7 kpc, that it is quite young (<~1000 yr). More details can be found in Renaud et al. 2010 arXiV 0910.3074 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#384 9 April 2010 |
Nespoli et al. 2010 accepted in A&A report the results
of K-band spectroscopy of 2 IGRs, IGR J16358-4726
and J16393-4643.
From the observations of CO absorption lines in their
spectra the authors re-classify the counterparts as late type
stars. They probably are K or M giants/supergiants.
With the X-ray results published on these two sources, they therefore conclude that both are in fact Symbiotic X-ray binaries, in contradiction with what had been suggested before. They also present arguments that lead them to select a mass function of 0.092 sol Masses and an orbit of 50.2 days for J16393-4643, and give an upper limit of 5 sol mass for the mass of the companion in this system. Of course this conclusion is valid only if in this source the IR counterpart is the one they analysed and not one of the other sources present in the X-ray error box More details in Nespoli et al. 2010 arXiV 0910.0990 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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#383 29 March 2010 |
Romano et al. 2010 ATel 2520 report the
observation of a new episode of outburst from
the SFXT IGR J08408-4503.
The outburst was first detected on 2010 March 28 at 15:53:38 UT by the BAT. The satellite was repointed to the source ~3ks after the BAT alert. The authors provide results of their spectral fitting of the BAT and XRT data. More details can be found in Romano et al. 2010 ATel 2520 while the BAT long term light curve can be found at http://swift.gsfc.nasa.gov/docs/swift/results/transients/weak/IGRJ08408-4503 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#382 22 March 2010 |
Rodriguez et al. 2010 accepted in A&A) report the possible identification
of 13 INTEGRAL sources, primarily thanks to observations made with Swift.
We first identify the possible X-ray counterparts to the IGR sources which allows us to provide a refined X-ray position for the 13 sources. This enabled us to find counterparts at longer wavelengths (IR, optical, and UV) from the online catalogs such as NED, 2MASS, USNO B1.0 and from the UV images obtained with the UVOT telescope for a majority of these sources. We finally made use of the X-ray spectral parameters obtained with the XRT in trying to identify the nature of those objects. The main results can be summarised as follows: We confirm the nature of 3 sources, identify 7 for the first time, and question the Swift/IGR association of 3 of the sample. -IGR J02524-0829 and J11457-1827 are confirmed as being AGN, the former is a Sey 2, and the latter is a Sey 1 -J08023-6954 is confirmed as being a RS CVn star -IGR J02086-1742, J12060+3818, J12070+2535, J13042-1020, and J13412+3022 are AGN, -IGR J14488-5942 is a probable X-ray Binary, -The association of IGR J03184-0014, with the Swift source is discussed but the the latter is an AGN. -IGR J15283-4443 is a probable Galactic source, whose nature is unclear -We question the association of IGR J11457-1827 and J23130+8608 with the Swift sources we have found, and further question the genuineness of the former IGR source. All details can be found in Rodriguez, Tomsick, Bodaghee 2010 at arXiV 1003.3741 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#381 12 March 2010 |
Following the recent Swift observation of IGR J17544-2619 (ATel: 2463, IGR Mail #380), Naik et al. (2010) report a near-infrared observation of this SFXT during its March, 2010, outburst. On March 7, 2010, or roughly 3 days after the X-ray flare, the source was observed in the J, H, and K bands at magnitudes 8.76(5), 8.27(4), and 8.20(4), respectively. The 1.2m telescope at Gurushikhar, Mt. Abu, India, will continue to monitor the source. Please see Naik et al. (2010, ATel: 2475) : ATel 2475 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#380 08 March 2010 |
Romano et al. 2010, announce results from Swift observations of the March 4, 2010,
outburst from the SFXT IGR J17544-2619. The last known activity from this source was in
August, 2009.
The peak of the outburst lasted ~150 s. The average source spectrum in the 15--150 keV band (from BAT) could be modeled by a power law with gamma = 3.4(8). XRT registered 25 cps at the peak and a spectrum in the 2--10 keV band that can be fit with a power law of gamma=1.2(1) and nH=1.2(2)e22 cm^-2. Correcting for absorption, the 2--10 keV flux is 2e-10 erg/cm^2/s. The bimodal shape of the peak is reminiscent of a previous flare from this source as well as from another SFXT, IGR J08408-4503. Please see Romano et al. (2010: ATel 2643) for more: ATel 2463 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#379 26 Feb. 2010 |
Kniazev et al. 2010, ATel 2457 report optical spectroscopy of
IGR J13168-7157, an IGR source from the new INTEGRAL
all-sky survey of Krivonos and collaborators (submitted,
online version at http://hea.iki.rssi.ru/integral/catalog)
The authors first provide a refined X-ray position of the source with SWIFT/XRT: R.A.=13h 16m 54.30s, Dec.=-71o 55' 23.7" (± ~5 arcsec) which is coincident with the ROSAT source 1RXS J131651.8-715537. They then identify 2MASX J13165424-7155270 (V=~16.3) as the IR counterpart of this source. Their spectrocsopic observations of this galaxy shows properties that are characteristic of Seyfert 1 AGN. They determine a redshift z=0.0705+/-0.0002. More details can be found in Kniazev et al. ATel 2457 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#378 24 Feb. 2010 |
Revnivtsev et al. 2010,
accepted in A&A report analysis of the
aperiodic optical variability of several CVs-IP with truncated
accretion discs, amongst which are IGR J00234+6141, J15094-6649,
J16500-3307 and J17195-4100.
The authors show that the optical power spectra of all sources
has the same shape, namely a broken power law with a
a shape P &alha; f-1 below a break frequency and
P αf-2 above.
They add that, in a model where the accretion disc is truncated by the magnetic field where the break frequency should correspond to the Keplerian frequency at the inner edge of the disc, all the source of their sample (but one) have inner disc close to corotation with the WD magnetosphere. In other word the break frequency is close to the WD spin. Exact values of the breaks are given for each sources. The authors further discuss their model and suggest an universal behaviour where the break frequency finally depends on the accretion rate in those systems. It could then be used to estimate the inner radius of the accretion disc and in turn the magnetic field. More details in Revnivtsev et al. 2010 arXiV 1002.4073 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#377 22 Feb. 2010 |
Stephen et al. 2010,
ATel 2441 report improved X-ray
positions of several IGRs from the last Bird's catalog.
By cross correlating the IGRs with the Rosat and XMM slew catalogs they could find the counterparts to: IGR J03502-2605, IGR J09453-2600, IGR J15409-4057, IGR J17488-2338 IGR J18482+0049, IGR J18538-0102, IGR J19475+0049 They further identify IGR J18538-0102 has a possible distant Galactic source or a background AGN whose alignment with G32.1-0.9 is coincidental. IGR J17488-2338 is an active radio galaxy detected behind the Galactic plane. More details including the X-ray positions can be found in Stephen et al. 2010 ATel 2441 Further to that, Halpern and Gotthelf report the analysis of an XMM observation of IGR J18538-0102. They provide a refine X-ray position of RA=18h53m48.50s, Dec=-01d02'30.0" (±3.2"). The X-ray spectrum can be fitted with a power-law model of photon index 1.7, NH = 1.5e22 cm-2. They find an object in the 2MASS Point Source Catalog at 18h53m48.48s, -01d02'29.6" with H=14.00 and K=12.50 More details can be found in Halpern and Gotthelf 2010 ATel 2445 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#376 5 Feb. 2010 |
Chen et al. 2010, accepted in A&A report the results of
their study of the type I X-ray bursts seen during the
2 outbursts of IGR J17473-2721.
The authors analysed the properties of 18 bursts 3 of which show photospheric radius expansion which allows them to estimate a distance of 6.4 kpc (with an estimated 15% error). They also find that the duration of the bursts are correlated with the luminosity expressed in ratio of the Eddington luminosity. Chen et al. also remark that at the end of the most recent outburst, the profile of the black body radius obtained through the fit of the spectra during the bursts, is anticorrelated with the bb temperature. The authors further discuss their findings in the context of type I bursts in LXMB and Atoll sources in general. More details can be found in Chen et al. 2010 arXiV 1002.1044 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#375 25 Jan. 2010 |
Degenaar et al. 2010, accepted in MNRAS report
the results of multi-instrumental observations
of 1RXH J17352.7-354013 associated with
IGR J17353-3539.
The detection of an X-ray burst from this source and the analysis presented in the paper, allow the authors to classify the source as a NS-LMXB. Thanks to the identification of a fading UV counterpart, the authors refute the formerly proposed UV counterpart, and provide a refine UV-IR position for the source : The J, H, Ks position is RA=17h 35m 23.74s Dec=-35deg 40' 16.6" (±0.1 arcsec) The authors present the spectral analysis of the source during and outside of the burst. They conclude that the source is a faint persistent LMXB, while the burst belongs to the untypical class of intermediately long bursts. They further discuss the physics of bursts in this source and in general. More details can be found in Degenaar et al. 2010 arXiV 1001.3688 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#374 05 Jan. 2010 |
Landi et al. 2010, ATel 2355 report the result of a Swift observation of IGR J14488-5942. They remark the presence of 2 X-ray sources within the IBIS error box, and favour the second and brightest as the most probable counterpart. It is located at RA= 14h 48m 43.33s Dec=-59d 42m 16.3s (±3.7 arcsec) It has a counterpart in the 2MASS catalogue with J ~15.5, H ~13.5 and K ~12.5 See Landi et al. 2009 ATel 2355 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Mail
#373 18 Dec. 2009 |
Nichelli et al. 2010, ATel 2354 report the detection of
X-ray pulsations in IGR J18173-2509.
The authors detected a periodic signal at ~830.7 in a Swift observation of the source. A re-analysis of a Chandra archival observation also showed a strong signal at about 1660s. The authors suggest that the true period of the source is the latter. The 1660s modulation was double peaked and, with a pulsed fraction ~50%. More details in Nichelli et al. 2009 ATel 2354 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#372 17 Dec. 2009 |
McBride et al. 2010, accepted in MNRAS report analysis
of 3 sources located in the Magellanic bridge amongst which an IGR source
recently discovered IGR J01572-7259.
This source has been associated with an USNO B1.0 source with B~15.5 and
R~15.5.
The Swift XRT light curve shows a clear pulsation at 11.57809pm2e-5 s The authors also make a joint XRT spectral analysis of the Swift and INTEGRAL data. The spectrum of the source is well fitted with an absorbed power law with a high energy cut-off, with Gamma=0.4 and an e-folding energy of 8 keV. The transient nature of the source coupled with their results (poulsation, hard spectrum,..) lead them to conclude that the source is probably a Be-HMXB. More details (including a discussion of sources belonging to the Magellanic bridge) can be found in McBride et al. 2010 arXiV 0912.2951 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#371 11 Dec. 2009 |
Sguera et al. 2010 accepted in MNRAS report
the analysis of archival XMM and INTEGRAL observations
of the SFXT IGR J18483-0311.
The XMM observation was taken at the lowest X-ray flux ever reported for this source, and the author conclude that this is its quiescent emission. The spectrum is well represented by an absorbed black body. The author add the INTEGRAL hard X-ray spectrum of the source accumulated outside the periods of activity to perform a broad band spectral study during quiescence. The overall spectrum is well fitted by an absorbed black body with a power law component: kT=1.40 keV, Gamma=2.0, Nh=3.4e22 cm-2. Note that a bmc model provides a good fit to the data. The author also report the possible detection of a cyclotron emission feature at 3.3 keV. This would lead to a pmagnetic field B~3-4e11 G, which is compatible with the value they derive using an alternative method. More details in Sguera et al. arXiV 0912.1730 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#370 Dec. 2009 |
Landi et al. (2010) analyzed archival Swift/XRT observations of the
fields of unclassified IGRs from the 4th IBIS Survey Catalog (Bird
et al., 2009) in order to provide (when possible) refined
positions, parameters from an absorbed power law fit the X-ray
spectrum, and classifications. Pertinent results are listed below:
IGR J00465-4005: AGN, R.A. (J2000) = 00:46:20.71, Dec. = -40:05:47.3, error radius = 4.26" nH ~ 24.1 (x10^22 /cm2), Γ ~ 2.49, F (2-10 keV) ~ 0.12 (x10^-11 erg/ cm2/s) IGR J07264-3553 (= LEDA 96373): Sey-2, R.A. = 07:26:26.19, Dec. = -35:54:21.3, error = 4.33" nH ~ 7.0, Γ ~ 2.55, F ~ 0.042 IGR J07506-1547: unclassified IGR J08262+4051: AGN candidate IGR J10447-6027: unclassified, R.A. = 10:44:51.62, Dec. = -60:25:10.6, error = 5.11" nH ~ 25.6, Γ~ 1.8 (fixed), F ~ 0.105 IGR J12123-5802: unclassified, R.A. = 12:12:25.97, Dec. = -58:00:23.1, error = 3.69" nH ~ 0.325 (Galactic), Gamma; ~ 1.26, F ~ 0.45 IGR J12482-5828: AGN, R.A. = 12:47:57.82, Dec. = -58:29:59.1, error = 4.02" nH ~ 0.92, Γ ~ 0.86, F ~ 0.41 IGR J13107-5626: AGN, R.A. = 13:10:37.27, Dec. = -56:26:56.7, error = 4.43" nH ~ 39.3, Γ ~ 1.8 (fixed), F ~ 0.11 IGR J14080-3023: Sey-1.5, R.A. = 14:08:06.57, Dec. = -30:23:52.6, error = 3.55" nH ~ 0.0362 (Galactic), Γ ~ 1.41, F ~ 0.64 IGR J17008-6425: unclassified, IGR J17331-2406: unclassified IGR J18134-1636: unclassified IGR J18175-1530: unclassified IGR J20569+4940: Blazar or muQSO, R.A. = 20:56:42.64, Dec. = -49:40:08.9, error = 3.55" nH ~ 0.53, Γ ~ 2.32, F ~ 1.19 IGR J22234-4116: AGN candidate, Their article includes details of the analysis, as well as uncertainties on the parameters. Please see Landi et al. (2009) accepted in MNRAS: arXiV 0912.1519 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#369 4 Dec. 2009 |
Wang 2010 accepted in A&A report on the analysis
of INTEGRAL observations of the Be-HMXB IGR J01583+6713.
The author did not find the potential pulse at 469s but
instead found a pulsation at 5.47 hr.
The IBIS spectra of the source can be well fitted with either a bremsstrahlung or a power law model. Wang also claims for the detection of cyclotron absorption features at 35 and 62-64 keV. The model parameters are in that case kT=45 keV fpor the bremss. or Gamma=2.11 for the power law (during the outburst). The author further discuss his findings and estimate a magnetic field B~4e12 G for the neutron star. He also comments on the expected position of the source in the Corbet diagram, and the positions or other long spin period Be systems in this diagram. More details can be found in Wang 2010 arXiV 0912.0337 Barragán et al. 2010 accepted in A&A report on a Suzaku observation of IGR J16318-4848. They can provide, for the first time, the most accurate broad band spectrum of the source, which allows them to confirm the high absorption (Nh=195e22 cm-2), measure the photon index with the highest accuracy (Gamma=0.676) and access the value of the high energy cu-off (20.5 keV). They also report the detection of several lines, iron Kalpha, Kbeta and Ni Kalpha in emission. They do not detect any compton shoulder, which probably indicates that the absorber is non-sperical and inhomogeneous. The authors remark significant variability of the source, but however mention that the hardness ratio remains stable which indicates only slight changes in the spectral shape of the source. Barragan and collaborators further discuss their findings and mention the possibility of a changing ionization structure of the wind between their observations and the previous ones, although other scenari are also envisioned. More details in Barragán et al. 2010 arXiV 0912.0254 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#368 2 Dec. 2009 |
Bozzo et al. 2010 accepted in A&A report on their first two weeks
of Swift monitoring of the new accreting ms pulsar IGR J17511-3057.
They detect occurrences of X-ray burst and they therefore provide
a separate spectral analysis of these and of the persistent emission.
The latter cannot be fitted by a single absorbed power law component, but always requires the addition of a second spectral component. A black body with temperature ~1 keV and radius ~3.6-6.3 km seems to be the best model. The author interpret this component as arising from the surface of the neutron star (the hot spots). The column density is compatible with the Galactic value on the line of sight. The spectral analysis of the burst do not reveal any photospheric radius expansion. The peak of the bursts are well fitted with a pure black body and have decay times of the order of 11-15 s. The authors further discuss their results and argue about the nature of the bursts which they think are most likely produced by the ignition of pure Helium. Based on this interpretation, and assuming the burst reach the Eddington luminosity they can derive an upper limit of ~10.1 kpc for the distance to the source. Bozzo and collaborators further add that the recurrence time of the bursts as observed with different satellites agrees well with that expected from nuclear burning of helium. More details can be found in Bozzo et al. 2010 arXiV 0912.0127 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#367 15 Nov. 2009 |
Chenevez et al. 2009
ATel 2298 report the detection of
a flare of IGR J19112+1358 with INTEGRAL/JEM-X.
IGR J19112+1358 was detected in the 3-10 keV JEM-X1 mosaic with a flux of 19.5 mCrab, and a 5-sigma upper limit of 8mCrab was derived in the 10-25 keV (JEM-X) range, while it is not detected with a 3-sigma upper limit of 5 mCrab between 20 and 40 keV (ISGRI). The detection of this flare allow them to refine the position of the source to RA= 19h 11m 22.3s DEC= +13d 55' 08.4" (± 1') This new position allows the authors to discards IRAS 19089+1351 as counterpart. No sources are found in the JEM-X error box while browsing online catalogs such as SIMBAD, NED, 2MASS extended source or NVSS, while several ones can however be found in the 2MASS point source catalog. More details in Chenevez et al. 2009 ATel 2298 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#366 9 Nov. 2009 |
Potter et al. 2009 accepted in MNRAS report the results of optical observations of the CV IGR J14536-5522 (SWIFT J1453.4-5524, 1RXS J145341.1-552146). Through rapid photometry and polarimetry the authors could refine the orbital period to 3.1564 hr. They also observed orbital circulary polarized modulation from 0 to -18% seen over 95% of the orbit, which they interpret as evidence for a single pole accretion. These results furthemore allow them to identify the source as a Polar. A QPO of period 5-6 minutes is also detected in the source optical light curve on specific occasion. Of particular importance is the detection of these QPO in circular polarimetry. This last point allow them to associate the QPO to the emission site at the cyclotron emitting shock region. More details can be found in Potter et al. 2009 arXiV 0911.1198 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail
#365 2 Nov. 2009 |
Torejón et al. 2009
detail recent NIR observations of 3 IGR HMXB candidates. The authors combined IR spectra from the I, J, H and K bands with JHK photometry to derive spectral types, luminosity classes, and distance estimations for the counterparts of these systems. The counterpart to IGR J18027-2016 is a supergiant star of spectral type B1 and luminosity class Ib, located at a distance of ~12.4 kpc. In IGR J18483-0311, the counterpart is a B0.5-B1 supergiant star with a likely luminosity class of Iab, which would place the system at ~2.8 kpc. For IGR J19140+0951, a B0.5 Ia supergiant star ~3.6 kpc away is proposed as the counterpart. They conclude that IGR J18027-2016 and IGR J19140+0951 are classical supergiant HMXBs while IGR J18483-0311 is a SFXT. For more information about these sources (and 2 others), please see Torrejón et al. (2009), accepted in A&A: arXiV 0910.5603 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #364 26 October 2009 |
Esposito et al. 2009 report on a Swift/XRT observation of
IGR J11215-5952, an SFXT with a known 165-d recurrence period that
is believed to represent the orbital period. On the expected date of its outburst (October 23, 2009) Swift observed the source for 2.2 ks and detected it at a mean count rate of 0.48(2) cts/s in the 1-10 keV band. The source spectrum was fit with absorbed (nH=1.2(3)x10^22 cm^-2) power law (Gamma=0.9(2)) which yields an unabsorbed luminosity of 2.4x10^35 erg/s. Please see Esposito et al. (2009): ATel 2257 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #363 22 October 2009 |
Bodaghee et al. 2009 report the first soft
X-ray spectrum of the X-ray pulsar IGR J01572-7259
(=IGR J015712-7259) based on a ~2-ks archival observation
with Swift/XRT.
The 0.5-7 keV spectrum can be fit with an absorbed, hard power law (gamma~0.9). The column density is ~4e21 cm^-2 which is larger than the expected line-of-sight absorption (by a factor of 5-10). This indicates that a small amount of material obscures the source in addition to any material in the Magellanic Bridge where this suspected HMXB is believed to be located. Assuming a distance of 55 kpc, the unabsorbed luminosity in the 2-10 keV range is ~4e36 erg/s. For more information, please see Bodaghee et al. (2009), ATel #2252: ATel 2252 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #362 20 October 2009 |
Rampy et al. 2009 accepted in ApJ, report on their Suzaku
observation of IGR J17544-2619.
Their observation lasts more than 60 hours during which the source show different states of activity. In particular an intense flare is seen with a flux 9000 times greater than during the first hours of observations. The authors separate the observation in several time intervals and do a spectral analysis of each. They remark that on long time scale the (averaged) photon index hardens with increasing flux, while the absorption seems to remain roughly constant. Looking on shorter time intervals, however, the situation is different since significant variation of Nh is seen. Rampy and collaborators discuss their results, and interpret the sudden increase of Nh they see as evidence for the presence of a dense clump in the wind of the companion. More details can be found in Rampy et al. 2009 arXiV 0904.1189 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #361 15 October 2009 |
Rodriguez et al. 2009 accepted in A&A report the results
of INTEGRAL, Swift, and RXTE observations of IGR J19294+1816.
The Swift observations allow us to refine the position to: RA=12h 29m 55.9s Dec=+18deg 18' 38.4" (+-3.5" at 90%). This in turn permits us to identify a possible infra red counterpart in the 2MASS catalogue. 2MASS J19295591+1818382 has J=14.56, H=12.99 Ks=12.11. The Swift and RXTE spectral analysis show that IGR J19294+1816 is a rather hard source, and we obtained evidence for local absorption in excess to the Galactic value in one of the observations. The timing study of the source allows us to identify an X-ray coherent pulsation at a barycentred period of 12.43781 s interpreted as the spin period of a pulsar binary. Our analysis point towards IGR J19294+1816 being an HMXB with a pulsar, while the values of the spin and orbital periods place it in the Be region of the Corbet diagram. The INTEGRAL archival data however show occurrences of short and intense flares which could indicate that the source is in fact an SFXT, hence a system with a supergiant companion. We discuss the implications of IGR J19294+1816 being a Supergiant HMXB instead of a Be-HMXB in terms of source evolution and possible links between the two types of systems. . More details in Rodriguez et al. 2009 arXiV 0910.2799 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #360 11 October 2009 |
Torres et al. 2009 ATel 2233, report the results
of new IR follow-up observations of IGR J17511-3057.
They confirm the association of the suggested IR
counterpart and the high energy source.
The source has faded significantly during their observations
to Ks> 18.8
More details in Torres et al.
ATel 2233
Further to that, Markwardt et al. 2009 ATel 2237
report that IGR J17511-3057 has significantly faded
also in the X-ray energy bands as seen with RXTE and
Swift.
More details in Markwardt et al. 2009
ATel 2237
I am happy to announce that the 4th IBIS catalogue has
now been accepted for publication in ApJS.
The catalogues contains 723 sources detected by IBIS of which
234 are new.
We will update the web site in the coming days/weeks, including all
new IGRs to the table.
All details about those sources are in Bird et al. 2009
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| Mail #359 9 October 2009 |
Miller-Jones et al. 2009 ATel 2232, report on their
radio observations of the ms accreting pulsar IGR J17511-3057.
The source was observed with the VLA in various configurations, at 8.46 GHz but was never detected. They derive 3-sigma upper limits of 0.16 to 0.18 mJy, which, after stacking all their observations, lead to an upper limit of 0.1 mJy. The authors discuss this lack of radio detection and conclude that, if the source is similar to other known ms pulsars, it should lie at a distance comparable to that of the Galactic centre. More details in Miller Jones et al. ATel 2232 I also take the opportunity of this mail to indicate the population study of hard X-ray emitting CVs published by Scaringi et al. 2009 accepted in MNRAS. The authors selected all hard CVs seen by INTEGRAL, Swift and one from a Suzaku observation, to study the global properties of this sample More details in Scaringi et al. arXiV 0910.0954 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #358 5 October 2009 |
Mason et al. 2009 A&A, 505, 281
report on the identification of the spectral type of the
companion in the system EXO 1722-363 (IGR J17252-3616).
Using the VLT/ISAAC IR spectrometer they determined that
the companion in this source is a B0-B1 Ia most likely
located at 8 kpc.
At this distance the authors add that the source has luminosities
in a range typical of those found in other sg HMXBs.
More details in Mason et al. 2009
A&A, 505, 281
Riggio et al. 2009 ATel 2221 report refined orbital parameters
for the ms pulsar IGR J17511-3057.
The authors remark that the pulsation is
present in all the RXTE observations of the source.
The raw (ie not bgd-corrected) pulse fraction is 12%.
They do not see any spin up/spin down trend, although
they remark some phase delays fluctuations.
They derive orbital ephemeris for the source of
Orbital period: 12487.5126 s, Projected semimajor axis: 275.194 lt-ms, Time of passage for ascending node: 55088.0320280 MJD, Eccentricity e: < 6e-5 (2 sigma c.l.) More details in Riggio et al. ATel 2221 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #358 2 October 2009 |
Papitto et al. 2009 ATel 2220 report the results
of an XMM Newton observation of the ms pulsar
IGR J17511-3057.
The authors give a position of the source that
is consistent with the one provided by Chandra.
The spectrum is fitted by a model composed of a multicolor disk black body with kTin=0.13 keV, a single temperature black body kT=0.73keV and a power law of with Gamma=1.71. They detecte the pulsation and their timing analysis reveals the source is spinning at a frequency of 244.8339512 Hz. Papitto et al. give an ephemeris of P_orb=12487.51 s, a sini/c=0.275196 lt-s, T*=55094.9695351 MJD where T* is the epoch of passage of the neutron star at the ascending node of the orbit. They in addition report the detection of X-ray burst and burst oscillations during these. For more information, see Papitto et al. (2009), ATel 2220 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #357 29 September 2009 |
Romano et al. 2009
report their monitoring observations of the SFXT IGR J18483-0311.
This is one of 2 SFXTs for which both a pulsation period (21s) and
an orbital period (18.5d) are known.
Swift provided the first (nearly-)continuous observation of an
SFXT during an entire orbital period. The authors measured a
quiescent luminosity of 2.3e33 erg/s which is the lowest level reported
thus far for this source. This is at least a factor 1200 lower than the
peak luminosity.
Romano et al. also tested whether there were variations of the spectral
parameters as a function of orbital phase. They did not find any significant
change in the parameters other than in the blackbody radius. This radius
is on the order of a few hundred meters, so the emission occurs very near
the surface (i.e. magnetic poles) of the neutron star. The authors conclude that the longterm lightcurve can be explained by the accretion of a homogeneous and spherically-symmetric wind along a highly-eccentric orbit. However, the large variations on short timescales can be interpreted as the result of accretion of an isotropic clumpy wind with clumps ranging in mass from 1e18 to 5e21 g. For more information, please see Romano et al. (2009), accepted in MNRAS: arXiV 0909.5109 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #356 28 September 2009 |
Nowak et al. 2009 ATel 2215 report the results
of their Chandra observation of IGR J17511-3057.
They first provide a revised source position to RA=17h 51m 08.66s Dec: -30deg 57' 41.0" with a 1sigma systematic error of 0.6". They discuss the 5" offset with the Swift position, and conclude that the pile up of the Swift rendered the uncertainty on the source position larger than the 3.5" reported in the Swift ATel. Nowak and collaborator also mention the presence of an X-ray burst during their observation. More careful analysis is on-going More details in Nowak et al. ATel 2215 Further to that, Torres et al , report on NIR observaiton of the same field. Their observations show a faint object at R.A=17h 51m 08.64s, Dec=-30deg 57' 40.70" therefore within the 0.6" Chandra position. They obtain a preliminar Ks=18.0. The authors discuss the variability and position of the source and conclude that the source is a viable counterpart for the millisecond pulsar. More details in Torres et al. ATel 2216 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #355 21 September 2009 |
Townsend et al. 2009 ATel 2202
report the results
of RXTE monitoring of IGR J01054-7253.
They observe a clear Doppler modulation of the 11.48s pulse period and a spin-up of this modulation. By fitting these data they could distinguish the spin-up rate from the orbital modulation. The best fit reveals an orbital period of 36.3 days and an average spin-up rate of 4.7 E-10 s/s. Townsend and collaborators add that a circular orbit model leads to a poor fit, which indicates that the orbit is eccentric. The best solution leads to a eccentricity of ~0.28. All these results are consistent with the source lying in the Be region of the Corbet diagram of HMXBs. More details in Townsend et al. 2009 ATel 2202 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #354 16 September 2009 | Watts et al. 2009 ATel 2199 report the discovery of strong burst oscillations during the type I X-ray burst of IGR J17511-3057 observed on Sept. 14th, 2009. Burst oscillation amplitude exceeds 10% rms in the 2-60 keV energy range. The authors do not detecte strong evolution in burst oscillation frequency during the burst, which is similar to what is seen in another source. Given the proximity of the burst oscillation frequency and the pulsation of the pulsar, the authors discuss the genuineness of these burst oscillation and conclude that both phenomena have indeed different origins More details in Watts et al. 2009 ATel 2199 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #353 15 September 2009 |
Bozzo et al. 2009 ATel 2198
report the results
of a Swift follow-up of IGR J17511-3057.
They first report the detection of a thermonuclear X-ray burst,
most likely an He burst, that makes the source belong to the
category of X-ray bursters.
The overall 2.5 ks spectrum of this period is well reopresented by an absorbed cut off power law (Nh=0.6e22 cm-2, Ecut~3.3 keV, Gamma~0.2). Using the last 1.5 ks of the observation, that were in the appropriate, mode of acquisition, the authors could refine the X-ray position of the source to: RA= 17h 51m 09.0s DEC: -30deg 57' 40.0" +-3.5" More details in Bozzo et al. 2009 ATel 2198 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #352 14 September 2009 |
Baldovin et al. 2009 ATel 2196
report the discovery
of a new source, IGR J17511-3057, with INTEGRAL/IBIS.
The source is detected in the 3-7, 7-11, 11-20 (JEM-X) and
20-40, 40-80 keV (IBIS) mosaics obtained between
2009-09-12 03:21:34 and 2009-09-12 05:27:22.
The best position is: RA=17h 51m 14.6s (267.811deg) DEC=-30deg 57' 14.4" (-30.954deg) +-2 arcmin The 3-100 keV joint JEM-X/ISGRI spectrum is well described by a power-law with Gamma~2.0, and a 3-20 keV flux (resp. 20-100 keV) of 5.7e-10 erg/cm2/s (4.8e-10 erg/cm2/s) More details in Baldovin et al. 2009 ATel 2196 Further to that, Markwardt et al. 2009 ATel 2197 report the detection of activity from a new 245 Hz pulsar (hence a ms X-ray pulsar), that they associate with IGR J17511-3057. The authors report that activity of this source was first detected on Sept. 11, but was initially attributed to 2 other known sources. Analysing an RXTE pointed observation toward this source the authors obtain a barycentred pulse frequency of 244.8337 Hz and an orbital period of 207.4 min. They derive a minimum mass of 0.13 Msol for the companion. Markwardt et al. further discuss the nature of the source. They first conclude, by comparison with Swift and Chandra observation of the field around XTE J1751-305 (a known source) that the IGR and XTE source are not the same. They add that the IGR source is more likely a normal LMXB. More details including the RXTE spectral results and a short comment on the proximity of two ms-pulsar in this region are given in Markwardt et al. 2009 ATel 2197 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #351 12 September 2009 |
Sanchez-Fernandez et al. 2009 ATel 2194 report the observation of
recent renewed activity from IGR J17586-2129 seen with Swift/BAT and
INTEGRAL/ISGRI. The source is detected by IBIS/ISGRI with with an average 18-40 keV flux of 11.2 mCrab in the combined observations from Aug 31 - Sep 6. The flux is rather stable over the last 2 weeks. The 18-150 keV spectra can be well fitted with a power-law with photon index of 3.0 +- 0.3. Assuming a stable spectrum since the Swift/XRT observation the authors suggest the presence of a cut-off in the spectrum in the 10-20 keV range. A cut-off power law also fits the spectrum well (Gamma=1.5 Ecut~20 keV), with a photon index consistent with that found with Swift/XRT. More details in Sanchez-Fernandez et al. ATel 2194 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #351 4 September 2009 |
Burenin et al. 2009 ATel 2193 report the results
of their optical observations of the counterpart of
IGR J18151-1052. Only one source (I~18.7) was found within the error box provided by Swift/XRT. The object is located at RA= 18h 15m 03.83s DEC=-10deg 51' 35.0" The spectroscopy reveals H_alpha emission line at zero redshift, which indicates that the object is a Galactic X-ray binary. The optical continuum is consistent with that of an absorbed OB-star. These results suggest that the system is a high-mass X-ray binary. More details in Burenin et al. ATel 2193 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #350 4 September 2009 |
Bozzo et al. 2009 ATel 2188 report the results
of a Swift follow-up observation of IGR J16442-5548.
The XRT observation allows them to give a refined
X-ray position. The source lies at RA=16h 44m 38.15s DEC=-55deg 50' 45.93" (+-4.1") The Swift/XRT spectrum is represented by a power law (Gamma=1.9) or a black body (kT=0.5 keV) with no absorption. The flux obtained with Swift is a factor 50 lower than that seen with INTEGRAL. The authors also remark that 2MASS 16443770-5550454 (J=10.953+/-0.033, H=10.341+/-0.031, K=10.175+/-0.027) and USNOB1 0341-0647474 (B2=12.95 R2=11.78, I=11.00) are both wihtin the XRT error box, and coincident within 1". More details in Bozzo et al. 2009 ATel 2188 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #349 3 September 2009 |
Bozzo et al. 2009 ATel 2185 report the discovery
of a new source IGR J16442-5548 with the IBIS
telescope onboarf INTEGRAL.
The source is found at RA=16h 42m 21s DEC=-55deg 48' 29" +-3.6 arcmin at 90% confidence The 20-100 keV ISGRI spectrum is well described by a power-law with Gamma~2.2, with a 20-100 keV flux of 1.2e-10 erg/cm^2/s. The authors also remark variability on a few hours time scale. More details in Bozzo et al. 2009 ATel 2185 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #348 2 September 2009 |
Zhang et al. 2009 A&A in press, report the results of INTEGRAL and
Swift observations of IGR J19405-3016. By clearly detecting the source in 1.4 Ms of INTEGRAL data at a 20-60 keV significance of 9.4 sigma, the authors first answer the question regarding the genuineness of the source raised by the low significance of its discovery in Bird's 3rd catalogue. This allows them to confirm the proposed associations with a Swift X-ray source and a Sey 1.2 AGN detected in Optical suggested in previous studies. Zhang et al. show that IGR J19405-3016 is rather steady in flux at hard X-rays, while it shows up to 39 % flux variations at soft X-rays. They study the spectral behaviour of the source : the joint XRT-ISGRI spectrum is well fitted by an absorbed power law with Nh=8.73e20 cm-2 and Gamma=2.11. They compare these results to the average values reported for Sey 1 AGN and discuss the origin of the possible differences they find. More details in Zhang et al. 2009 arXiV 0909.0075 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #347 1 September 2009 |
Krimm et al. 2009 ATel 2156 observed an outburst
from a source possibly coincident with IGR J17586-2129.
The source lies at RA=17h 58m 34.56s Dec= -21deg 23' 20.82" with an estimated error of 4". The authors also discuss the associations of the Swift and INTEGRAL sources, find IR counterpart and discuss the possible type of the source. See ATel 2156 Krivonos et al. ATel 2170 report the discovery of 2 new IGRs IGR J18151-1052 and IGR J17009+3559. These sources have been observed with Swift: IGR J18151-1052 R.A.=18h15m03.99s, Decl.=-10d51m31.81s, (+-4.2 "). No counterpart found in catalogue although a faint source apparently seen in DSS II R plate. IGR J17009+3559 R.A.=17h01m53.1617s, Decl.=35d59m51.33s, (+-5" ). The optical counterpart is the galaxy 2MASX J17005297+3559560. Optical observations of this object reveal that it is a XBONG. See ATel 2170 for many more details Barthelemy et al. ATel 2178 report the observation of a new outburst from the SFXT IGR J08408-4503 and give the details of this episode. See ATel 2178 In addition, Zhang et al. 2009, A&A, 502, 231 report the analysis of 2 periods of outburst of IGR J17473-2721 as seen with RXTE and Swift. They separate the outburst in different sequences based on the hardness and flux of the source and provide spectral analysis of them. They then discuss their findings in the context of state evolution of X-ray binaries See the paper here Clark et al. accepted in MNRAS report the discovery of an orbital period of 4.926 days in the SFXT IGR J17544-2619. They also obtain an upper limit on the radius of the supergiant of R< 23 Rsol. See arXiV 0907.3544 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #346 July 16 2009 |
Mescheryakov et al. 2009 ATel 2132 report the
result of optical observations of 2 IGRs. The sources are
IGRJ17476-2253, and J12107+3822.
Both object are classified as Sey 1 AGN.
The first is at a redshift z=0.0463, and the second
at z=0.0228
More details in Mescheryakov et al.
ATel 2132
I would also like to mention the publication and/or acceptance
of the following articles that deal with IGRs:
-Romano et al. accepted in MNRAS
arXiV 0907.1289
report the results of their first year of Swift monitoring of 4 SFXTs
The followings are studies of families of sources including IGRs
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| Mail #345 June 29 2009 |
Heinke et al. 2009 report their results of Chandra, XMM, and
Suzaku observations of IGR J17407-2808.
They propose that CXOU J174042.0-280724 is the soft X-ray counterpart to IGR J17407-2808 given their similar variability in flux and column density (~ 1.7x10^22), as well as their hard spectra (gamma ~ 0.9). The best X-ray position is R.A. (J2000) = 17h 40m 42.05s Dec. = -28deg 07' 24.6" (+/- 0.7 arcsec). Periodic pulsations are not detected, and there are no known optical/IR counterparts compatible with the error circle and X-ray properties. The authors suspect that the source consists of a neutron star or black hole primary, but the companion's nature is a mystery left to be resolved (hopefully) by additional observations. More information can be found in Heinke et al. (ApJ in press): arXiv 0906.4743 Romano et al. 2009 announce that Swift observed the end of an outburst from the SFXT IGR J18450-0435. The observation occurred ~800s after the initial flare. The light curve displays a decay in flux. A power law fit to the 15-150 keV spectrum yields gamma ~ 2.4 and a time-integrated flux of 1.1(2)x10^-6 erg/cm2. Details of the observation are in Romano et al. : ATel 2102 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #344 June 23 2009 | Corbet et al. 2009 ATel 2092 report the results of RXTE observations of the recently discovered INTEGRAL source IGR J01054-7253. They find pulsations at a period of 11.483 s in the power spectrum, with several harmonics. The pulse profile is complex with multiple peaks. More details in Corbet et al. 2009 ATel 2092 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #343 June 22 2009 |
de Martino et al. 2009 ATel 2089 report the preliminary
results of XMM observations of the CV IGR J21237+4218.
They find a strong pulse period at 743.2 sec with a pulse fraction of 55%. They also detect this periodicity in the OM data, and mention that the X-ray pulse is anti-phased with that in the optical. These pulsation lead them to classify the source as a secure member of the Intermediate Polars. de Martino et al. provide results from their spectral analysis. The best composite 0.2-10keV spectrum consists of a blackbody with kT= 56eV, a thermal plasma at kT=16keV, and a Gaussian at 6.4keV with an equivalent width of 159eV. All these emission component are absorbed by a a complex absorption consisting of a partial (69%) covering component with Nh=1.1x10^23 cm^2 and a total absorber with Nh=5x10^21 H-atom/cm^2. More details in de MArtino et al. 2009 ATel 2089 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #342 June 18 2009 |
Coe et al. 2009 ATel 2088 report the results of Swift/XRT
observations of IGR J01054-7253.
The XRT allows them to refine the position to
RA=01h 04m 41.41s Dec=-72deg 54' 04.6" (+-3.6 arcsec). This position lies within 3.5 arcsec of the V=14.8 star [M2002] SMC 59977 which seems to be a variable object in the I band with 1year long outburst typical of Be star in the SMC. The Swift data show evidence for a periodicity at 17.49s with a single-peaked sinusoidal pulse profile. The authors propose that IGR J01054-7253 is a new High Mass X-ray Binary in the SMC More details in Coe et al. ATel 2088 In a recently accepted and published paper, Morris et al, 2009, ApJ, 699, 892 report the results of Suzaku observation of 4 high energy sources, 3 of which are IGRs (16195-4945, 16465-4507, and 16493-4348). They provide X-ray spectral and temporal analysis of the sources, and in one case separate the observations in several intervals due to the presence of a short flare. The analysis allow the authors to conclude that the four sources are heavily absorbed HMXB, confirming the previously proposed identifications of J16195-4945, and J16465-4507, and providing a new identification of 16493-4348. In the case of J16195-4945, where the flare is seen, the authors models of accretion around supergiant stars, and mention the possible presence of a disk around the donor star. Using this model they can estimate a tentative orbital period of about 16 days. Morris et al. discuss their findings in the context of wind accretion and scenarios linking SFXTs to Sg-HMXBs, More details in Morris et al. 2009 arXiV 0808.3141 (submitted version only) Molina et al. 2009 accepted in MNRAS report the results of high energy analysis of a complete sample of Type 1 AGN seen by INTEGRAL. This includes a certain number of IGRs, and for each source the spectral parameters of broad band X-ray spectral analysis are given. More details in Molina et al. 2009 arXiV 0906.2909 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #341 June 16 2009 |
Tomsick et al. 2009 accepted in ApJ
report the results of Chandra observations of
the field around 22 IGRs. They find the likely counterparts
of 18 of these sources. The site is updated with the
refined positions. The authors provide the results of the Chandra spectral analysis of the sources and discuss their possible types. 2 sources are probable SNRs: IGR J14003-6326 and J17448-3232 2 sources are X-ray binaries, and 5 are are XRB candidates: J14331-6112 is an HMXB, and J17404-3655 which the authors suggest is an HMXB (rather than an LMXB) J16287-5021, J17354-3255, J17505-2647, J17586-2129 are candidates HMXB 3 sources are CVs and one is a candidate CV J19267+1325, J18173-2509, J18308-1232 J15529-5029 may be a CV 1 source is an AGN, and 2 are candidates J14471-6414 is an AGN (confirmation of the association with a Sey 1.2 at z=0.053) J19443+2117 and J18485-0047 are candidates 2 sources were not classified (J11098-6457 and J18134-1636), while no counterparts were detected for 4 sources which may indicate that they are transient or variable sources Much more details, especially an estimate of the probability of spurious associations can be found in Tomsick et al. 2009 arXiV 0906.2577 Reig and Zezas 2009 ATel 2085 report the results of their spectroscopic observation of the optical counterpart to IGR J06074+2205. The 4000-5000 A spectrum is dominated by H neutral He, which indicates an O or B star. Further consideration on the strenght and presence of other lines lead them to classify the star as a B0.5V although they mention that a B1V cannot be ruled out. The authors add that the Halpha line is highly variable, both in strength and shape. This indicates global changes in the structure of the equatorial disc. More details (lines) can be found in Reig and Zezas 2009 ATel 2085 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #340 June 12 2009 |
Bozzo et al. 2009 report the discovery of a new source
with the INTEGRAL satellite.
IGR J01054-7253 was detected in observations performed
between 2009-06-07 05:26 and 2009-06-11 08:00 UTC
at Ra=01h 05m 27s Dec=-72deg 53' 33" +- 3.5' at 90% The source position is compatible with being in the SMC The IBIS/ISGRI spectrum is best represented by a simple power law model with Gamma=2.5 at a flux of ~3 mCrab. Bozzo et al. add that JEM-X provides a marginal (4-sigma) detection. They also remark that RX J0104.7-7253 lies within the INTEGRAL error box. By performing a comparison of the fluxes obtained with each of the two instruments they conclude that the Rosat source is not the counterpart of IGR J01054-7253, unless the latter is strongly variable. More details in Bozzo et al. 2009 ATel 2079 ATel 2079 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #339 June 11 2009 |
Grupe et al. 2009 report the detection of a flare
from IGR J16328-4726 with Swift/BAT on June 10
2009 at 07h54:27 UTC.
The Swift/XRT observation, begining about 6 minutes after
the detection of the flare, allowed a fine X-ray position to be
found. The source lies at RA= 16h 32m 37.88 s Dec= -47deg 23' 42.4" with an uncertainty of 1.7" at 90% The authors add that the source is steadily decaying over the first orbit of observation. The spectrum of this interval can be fitted wuth an absorbed power law with Gamma=0.56 and Nh=8.1e22 cm_2. Grupe and collaborator finish indicating that they did not find any USNO-B1 counterparts, but one 2MASS counterpart is found at : RA, Dec (J2000)= 16 32 37.91, -47 23 40.9 with J=14.631, H=12.423, K=11.275. More details in Grupe et al. ATel 2075 Capitanio et al. 2009 accepted in MNRAS present the results of observations of H1743-322 (IGR J17464-3213) during a failed outburst in October-November 2008. All details can be found in Capitanio et al. 2009 arXiV 0906.1137 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #338 June 8 2009 |
Romano et al. 2009 ATel 2069
report the detection of a new period of outburst of
the SFXT IGR J17544-2619 with Swift.
The peak of the outburst has a hard spectrum, fitted with a power-law model with Gamma=1.12, and NH=1.2 E+22 cm-2. The spectrum taken later during the outburst is also fitted with a power-law with Gamma=1.10 and NH=1.3E+22 cm-2. More details in Romano et al. ATel 2069 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #337 June 5 2009 |
Bozzo et al. 2009 accepted in A&A report the
results of a Swift observations of the SFXT
IGR J16479-4514 during an outburst in 2009, january
and compare them to previous outbursts.
The main result of this study can be summarised as
follows: The authors remark that the onset of the 2005, 2008 and 2009 outbursts (measured with Swift/BAT) occur respectively at orbital phases 0.36, 0.3654 and 0.36, i.e. the outburst precede the eclipse. They interpret this as an evidence that the outburst, although rare, are connected to the orbital phase. More details about the observations, data analysis and interpretation of the results can be found in Bozzo et al. 2009 arXiV 0906.0883 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #336 June 1st 2009 |
Giunta et al. 2009, in an article to be published in MNRAS, describe
observations of the SFXT IGR J18483-0311 during quiescence.
The authors combined an 18-ks observation from XMM (14.4-ks of
effective exposure time) with a 1.2-ks observation from Chandra
and archival data from Swift.
An improved X-ray position for the source is provided thanks to
Chandra: R.A. = 18h 48m 17.2s Dec.=-03d 10' 16.8" with an error of 0.8". This is compatible with the position obtained for the optical counterpart (Rahoui et al. 2008). This represents phase 0.24 of the orbital period. The 0.5--10 keV XMM/EPIC-PN spectrum can be fit with an absorbed power law with nH=7.7(-0.8+1.2)x10^22 /cm2 and a photon index of 2.5(3). In this energy range, the absorbed and unabsorbed fluxes are 9.3x10^-13 and 5.2x10^-12 erg/s/cm2, respectively. This translates to a luminosity of 10^34 erg/s assuming a distance of 4 kpc (Rahoui et al. 2008). The upper limits on the equivalent widths of potential iron lines at 6.4 and 6.7 keV are 0.17 and 0.10 keV, respectively. This observation corresponds to the 0.52 phase of the orbital period. An absorbed power law fit to a 7-ks Swift observation from February 2006, yields nH=6.0(-1.6+1.9)x10^22 /cm2 and a photon index of 1.4(5) in the 0.5--10 keV range. This observation corresponds to the 0.67 phase of the orbital period. Timing analysis of the PN data reveals a 3-7-sigma detection of a spin period of 21.033(4)s which agrees with the spin period detected in INTEGRAL data by Sguera et al. 2007. The pulse fraction is 15(3)% with a sinusoidal profile. Note that this fraction is a factor 3 lower than the value measured during the outburst (albeit in slightly different energy bands). The authors discuss this source in the context of other SFXTs, in particular SAX J1818.6-1703 which has a similar orbital period. They provide an analysis of the X-ray variability as a function of orbital phase. They suggest that the changes in the X-ray flux could be due to changes in the accretion rate rather than due to eclipsing events. By comparing the pulse period from XMM and INTEGRAL observations, Giunta et al. also noticed variations in the spin period: they measure a spin-period derivative of -1.3(3)x10^-9 s/s. The quality of the data do not allow the authors to pinpoint the cause of the changing spin. They believe the effects of the travel-time of light in the binary are the primary cause but they can not rule out accretion torques acting on the NS. More information about the study can be found in Giunta et al. 2009, to appear in MNRAS arXiV 0905.4866 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #335 May 25 2009 |
Zurita Heras et al. 2009accepted in A&A report
the identification of IGR J09026-4812 as a Seyfert
galaxy of type 1. New optical and infrared observations with the ESO/NTT telescope have allowed them to confirm that 2MASS J09023731-4813339 is the counterpart of IGR J09026-4812. The NIR images in JHKs revealed an extended source, excluding any Galactic compact source possibility as previously proposed. The source spectrum shows three main emission lines identified as the HeI lambda 1.0830 micron line, and the HI Pa_beta and Pa_alpha lines, typical in galaxies with an active galactic nucleus. The broadness of these lines reached values as large as 4000 km/s pointing towards a type 1 Seyfert galaxy. The redshift of the source is z=0.0391(4). More details can be found in Zurita Heras et al. 2009 arXiV 0905.3309 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #334 May 19 2009 |
Sidoli et al. 2009accepted in MNRAS report
the results of Swift observations of 3 SFXTs:
IGR J17391-3021 (XTE J1739-302), J17544-2619,
J08408-4503.
Their main results of analysis during flaring periods for those sources can be summarised as follows: J1739-302: Time resolved spectroscopy of the flaring event of 2008 August 13 reveals that the spectra are well fitted with eithe an absorbed power law or absorbed black body. While the value of the photon index or the black body temperature remain constant throughout the flare, there is a clear evolution of the absorption column density: NH is higher during the rising portion of the flare. More complex spectral models such as the bmc are also used and provide a good representation of the spectra. In that case the authors estimate a bb temperature (of the seed photons) of 1.6 keV for a black body size of 1.6 km, that is consistent with the size of the polar cap. J17544-2619: The flare of Sept 4, 2008 seems softer than the ones previously observed in this source. It is well fitted by either an absorbed power law or an absorbed black body. Sidoli et al. mention that the latter model provides a better representation of the spectrum with kTbb found between 1.5 and 1.8 keV, and a radius of 1.3 km again said as being comaptible with the size of the polar cap. J08408-4503: The specrea are well fitted with models of cut off power law or power law with black body emission with little absorption. In this case there seems to be clearly two population of photons, as a fit with a bmc model need the addition of a black body to account for soft X-ray emission at 0.3 keV. The authors cannot distinguish which of the two population is the source of the seed photons for comptonization, and discuss the two cases. They then discuss the results obtained for these 3 sources in the context of SFXTs in general, and compare the results to the models proposed for these objects: clump accretion and equatorial wind of the SG star. More details can be found in Sidoli et al. 2009 arXiV 0905.2815 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #333 May 11 2009 | Anzolin et al. 2009 present detailed timing and spectral analyses of XMM and INTEGRAL observations of the intermediate-polar cataclysmic variable IGR J00234+6241. Roughly 26 ks of XMM data and almost 7 Ms of INTEGRAL data were used for the analysis. The authors provide an updated spin period of 561.64(56)s for the white-dwarf primary (see also Bonnet-Bideau et al. 2007). This pulsation period is detected only below 2 keV, with a significant signal also present at 2P. While they detect the ~1hr psuedo-periodic variation that was seen in the optical data, the significance of the detection above 1keV is less than 3sigma. The source is hard with emission detected up to 90 keV. The 0.3--100 keV broadband spectrum is described by a multi-temperature plasma-emission model whose maximum temperature is ~50 keV. An iron line is detected at 6.4 keV. The absorption is consistent with the expected interstellar value, although a dense intrinsic absorber partially covering the source can not be ruled out. The mass of the white dwarf is estimated at ~0.91 solar masses. For a distance of 500 pc, the lower limit for the magnetic dipole moment is ~10^32 G cm^3, suggesting that the WD is not strongly magnetized and that it is not spinning at its equilibrium period. Please read Anzolin et al. 2009 (accepted for A&A) for more information: arXiV 0905.1080 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #332 April 27 2009 |
Zolotukhin 2009 ATel 2032 report the analysis of ESO-NTT
archival data of the field of IGR J17254-3257.
He reports that a single point source located within the XMM error box can be seen in the I-band image. Its estimated coordinates are : R.A.=17h 25m 24.85s, DEC=-32deg 57' 16.5" (+-0.2" uncertainty in the reference frame of 2MASS), Zolotukhin also reports I = 19.1 He, however, adds that there is another I=19.7 object 2.7" away from the centre of XMM-Newton position that cannot be completely ruled out as the counterpart. More details in Zolotukhin 2009 ATel 2032 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #331 April 23 2009 | Saxton et al. 2009 ATel 2027 report detection of IGR J17375-3022 with XMM while performing a slew on 2009-04-01 16:00:00 U.T. The source was detected at a position RA=17h 37m 33.2s Dec= -30deg 23' 14" +- 8" at 1 sigma The authors infer a 2-10 keV flux of 9.8 e-11 erg/cm2/s, slightly higher than the flux previously reported from Swift observations/ More details in Saxton et al. 2009 ATel 2027 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #330 April 20 2009 |
Bulgarelli et al. 2009, ATel 2017, report the detection of
a possible gamma ray transient with AGILE.
The source, labeled AGL J1734-3310, has gamma ray
coordinates that are consistent with the INTEGRAL source
IGR J17354-3255, although the authors report that
no counterpart is detected with the super Agile hard X-ray
detector in the 20-60 keV flux.
Further to that Vercellone et al. 2009 ATel 2019,
report the results of a Swift observation of the same field.
They find 2 sources within the INTEGRAL error box. Due to the
persistence of the second source, they suggest that the first is
the counterpart to the IGR source. Its refined position is RA= 17h 35m 27.16s DEC= -32deg 55' 48.9" +-3.7" at 90%. They remark that the flux increases by a factor of about 10 in 7 hours. The spectrum is well fitted by an absorbed black body with Nh=5e22 cm-2 and kT=1.4 keV, for an unabsorbed 0.3-10 keV flux of 1.1e-11 erg/s/cm2. Tomsick 2009 adds to that the results of a Chandra observation of the same field. Two sources are also detected in the error box of IBIS, and although the positions obtained with Chandra are slightly outside the Swift error boxes, he suggests that the sources are the same. Tomsick adds that his analysis lead him to agree with Vercellone that source 1 is the counterpart to the IGR source. Its Chandra coordinates are: R.A. = 17h 35m 27s.59, Decl. = -32d 55' 54".4 +-0.64" This is within 0.2 arcseconds of 2MASS J17352760-3255544, which has J=12.51, H=10.99, and Ks=10.27. This source does not appear in the USNO optical catalogs, suggesting a relatively high level of extinction. The 0.3-10 keV spectrum is well-described by an absorbed power-law with Nh= 7.5e22 cm^-2 and Gamma= 0.54. The flux is similar to that seen by Swift, although the spectrum is not necessarily thermal. Tomsick adds that the high level of extinction and the position within 5 degrees of the Galactic plane may suggest a distance of 8.5 kpc, therefore a luminosity of ~1e35 erg/s. All these results may indicate the source is an HMXB. More details in Atels 2017, 2019, and 2022 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #329 April 14 2009 |
Zhang and collaborators, in an article published in A&A,
describe their observations of IGR J16460+0849 by INTEGRAL
and Swift.
Analyzing all available public data from ISGRI up to August 25, 2006 (511 ks), the authors find that the source is detected at the 4.4 sigma level in a ~19 ks observation taken between March, 2003, and September, 2004. Thereafter, however, the source is no longer detected despite accumulating ~271 ks of exposure time. This suggests that the source, whose average flux is 9 mCrab when detected, varies on timescales of years. A power law fit to the 20-100 keV spectrum yields a photon index of 1.45+/-0.86. A 5-ks snapshot by Swift/XRT showed no source detection in the ISGRI error circle, even though an extrapolation of the ISGRI spectrum would lead us to expect a bright X-ray source in the Swift's energy range. The authors construct the significance distribution of the mosaic images in which the source is detected to show that the probability of a 4.4-sigma detection drops to around 3.5 sigma. Nevertheless, the authors conclude that the source is real given that it is detected in the mosaic images from 3 subsequent observations taken over a period of 1.5 years, that the data from 3 energy bands provides a well-fitted power-law spectrum, and that the source remains detectable in mosaic images with different offset angles whereas the noise structures fluctuate. The position of the source at high Galactic latitudes hints at an extragalactic source. However, unlike a typical AGN, increased exposure time does not lead to an increase in the significance of the detection. The source is variable and spends a majority of its time in an inactive state with a flux that is below the Swift and ISGRI detection thresholds. Further information can be found in Zhang et al,, A&A, 497, 347, 2009. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #328 April 7 2009 |
Corbet & Krimm, 2009 ATel 2008, report the analysis
of the Swift/BAT light curve of IGR J19294+1816 covering the
period Jan 1st 2006 to April 2 2009. They report a strong peak in the powe spectrum of the source at a period of 117 days, that they associate with the orbital period of the source. They also discuss the occurrences of high flux at half this period, and suggest a interaction of the neutron star with the disk of the donor star. They derive ephemeris as follows Tpeak (MJD) = 54,680.3 (+/- 0.6) + n x 117.2 (+/- 0.2) The object lies in the region of Be systems in the Corbet Diagram. This is also compatible with the transient nature of this system. More details in Corbet & Krimm ATel 2008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #327 April 2 2009 |
Strohmayer et al., 2009 ATel 2002,
report the results of RXTE observations of IGR J19294+1816.
They detect strong pulsations with a barycentric period of 12.44s.
The amplitude during one of the observation is 37%.
This confirms that the object is most likely an accreting pulsar.
The authors add that the phase-averaged flux from the source
is highly variable, with a mean intensity corresponding to a flux of
~2 mCrab in the PCA band.
The phase-averaged variability may be quasiperiodic, with variations on
a time-scale near 190 seconds.
The energy spectrum is well modeled by a power law, with photon
index in the range 1.5 - 1.9, and an iron line at 6.4 keV.
More details in Strohmayer et al.
ATel 2002
Prat et al. 2009 ATel ATEL #2003 report renewed activity of
the Black-Hole Candidate IGR J17098-3628 seen with INTEGRAL/IBIS/ISGRI
between 2009-03-30T14:14 to 2009-03-31T11:11. The source was not detected during recent Galactic Bulge observations with a typical 3 sigma upper limit of about 7 mCrab in the 18-40 keV band. Possible activity can be seen in the RXTE/ASM light curve show a possible activity since 2009-03-25. The ISGRI spectrum can be represented by a simple power law model with photon index ~2.0 suggestive of a hard state of a BHC. The authors conclude that the source is entering a new period of outburst More details in Prat et al. 2009 ATel 2003 Jain and collaborators, 2009 accepted in MNRAS report the results of Swift/BAT and RXTE/ASM observations of the SFXT IGR J16479-4514. They detect a strong modulation of the 18-50 keV BAT light curve at 3.32 day that they attribute to the orbital period of the system. This period is less evident in the ASM data, but still significant once the light curve is folded. They also mention the presence of a 0.6d eclipsing phase in the light curves from both observatory. The fact that the eclipse is seen at the same phase with both instruments strengthens the interpretation of an eclipse. The authors further discuss their findings in the context of models explaining the behaviour of SFXTs. More details in Jain et al. arXiV 0903.5403 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #327 April 1 2009 |
Krimm et al., 2009 ATel 1999,
report the detection of the
recently discovered INTEGRAL source IGR J19294+1816
in archival data of Swift/BAT.
The earliest detection reported was on January 13, 2006, and the authors report a total of 6 additional detections since then. They also report an recent increased activity seen on March 23, 2009 (NOT 2008 as reported in the ATel), and it seems that after March 28 the source has faded below detectability. The authors mention a possible sort of periodicity in the system at a period of ~56 days as seen from the period of detections with the BAT. More details in Krimm et al. 2009 ATel 1999 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #326 March 31 2009 |
Tuerler et al., 2009 ATel 1997, report the discovery
of a new source IGR J19294+1816 during INTEGRAL
observations of the field around GRS 1915+105 performed on
2009-03-27 from 11:56 UT to 17:43 UT
The source is located at R.A.=292.42 deg, Dec=+18.28 deg
(+- 3 arcmin @68% confidence).
It is well detected in the 20-40 keV mosaic image at a flux of ~14 +/- 2 mCrab, but not at higher energies. It was not detected in either of the two previous INTEGRAL observations of the same field taken on 2009-03-18 and 21 with a 3-sigma upper limit of about 6 mCrab (20-40 keV). The time-averaged spectrum of the source is consistent with a single powerlaw in the 18-50 keV range with a rather steep photon index of Gamma = 4.0 +/-0.7. The model flux in the 20-40 keV band is of 1.1 E-10 erg/cm^2/s. The authors report the presence of the Einstein source 2E 1927.5+1805 at ~5 arcmin from the IBIS position, and they do not exclude an association of IGR J19294+1816 and 2E 1927.5+1805. More details in Tuerler et al. 2009 ATel 1997 Further to that we (Rodriguez et al. 2009, ATel 1998), analysed Swift archival observations of the field around this new source, performed on 2007 december 9 and 13. A bright source is found within the 90% confidence limit of IGR J19294+1816. The best XRT position is RA= 19h 29m 55.9s Dec=+18deg 18' 39" (+-3.5" at 90%). This source is also labeled Swift 1929.8+1821 and has a position inconsistent with that of the 2E 1927.5+1805. A single 2MASS point source lies in the XRT error box: 2MASS J19295591+1818382 with infrared magnitudes J=14.56 +-0.03, H=12.99 +-0.02 and Ks=12.11+-0.02. The 0.5-10 keV Swift spectrum is well fitted with an absorbed power law (chi square 1.0 for 49 d.o.f.), or an absorbed black body. with N_H=3.7e22 cm-2, Gamma=0.8, and a 2-10 keV unabsorbed flux of 3.6e-11 erg/s/cm-2 for the former model, and kT_bb=2.1 keV and an unabsorbed 2-10 keV flux of 3.0e-11 erg/s/c for the latter. The size of the emitting black body (as returned from the fit) is R=(0.46 * D_10) km where D_10 is the distance to the source in units of 10 kpc. We also report the presence of a feature at 8.0e-2Hz in the power spectrum. This feature could be a coherent pulsation although we do not see any particularity in a light curve folded at this period. We further discuss our results and suggest thay IGR J19294+1816 is more likely associated to the swift source (Swift J1929.8+1821), and suggest that it may be a possible X-ray binary possibly containing a pulsar. More details in Rodriguez et al. ATel 1998 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #325 March 24 2009 |
Blanchard et al.,
ATel 1981 report the discovery
of this source with INTEGRAL IBIS and JEM-X at RA=277.114, DEC=-3.764.
Follow up observations with Swift have allowed them to
refine the X-ray position to RA=18 28 30.00 Dec=-03 45 43.2 with an uncertainty of 4arcsec. The joint INTEGRAL-Swift spectrum is well fitted by a black body with a temperature of 4 keV. These authors did not find any counterpart in the UVOT U,V and B fitler and in the POSS II survey either. More details in Blanchard et al. ATel 1981 while images and spectra can be found here (courtesy V. Beckmann) Further to this Halpern and collaborators 2009 ATel 1982, mention that they failed to find a counterpart in the I-band down to a limiting magnitude of I=20. These authors also re analysed the Swift data and managed to obtain Nh=2.4e22 cm-2 in a rather good agreement with the high optical extinction in this direction. With this absorption the bb temperature is 2.9 keV. They also remark that other model fit the data well (power law or bremsstrahlung) with higher values of Nh. The Swift XRT light curve shows variability by a factor of 2 on time scales as short as 100 s. Finally Halpern et al. mention the presence of a faint XMM source at a postion consistent with the Swift one, and suggest that it is the quiescent counterpart to the IGR source More details in Halpern et al. ATel 1982 while the light curve can be found here (courtesy J. Halpern) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #324 March 12 2009 | Sguera et al., 2009, accepted in ApJ study the possible association of AX J1841.0-0536/IGR J18410-0535 with either 3EG J1837-0423 or HESS J1841-055. Although a good positional match between the HESS and the X-ray source may indicate that they are associated, the fact that the HESS source is extended and non-variable lead the authors to suggest that the AX/IGR source cannot be responsible for the entire TeV emission. The AX/IGR source is, on the other hand, only marginally positionally consistent with the Egret one. The variability and behavior of the 2 sources lead them to suggest a possible association. The authors further study the physical conditions under which the AX/IGR source could emit MeV flares and/or TeV emission. They suggest a theoretical scenario where the AX/IGR source contains a pulsar with a low B, which undergoes sporadic changes to transient Atoll-states. There a magnetic tower could produce transient jets and high-energy emission. More details in Sguera et al. 2009 arXiV 0903.1763 Krimm et al. 2009 ATel 1971, report the detection of an outburst from the SFXT IGR 17544-2619 with Swift/BAT. This outburst was apparently composed of several periods of flaring activity. More details in Krimm et al. ATel 1971 while the BAT light curve is available at http://swift.gsfc.nasa.gov/docs/swift/results/transients/weak/IGRJ17544-2619/ | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #323 March 12 2009 |
Butler et al., 2009, accepted in ApJ
report the results of optical spectroscopy of 5 IGRs.
The sources in question are IGR J16426+6536, J18214-1318,
J18308-1232, J19267+1325 and J22292+6647.
For each sources they first identify the optical/IR counterpart(s) based on the refined (<10" error box) X-ray position of the source published in other studies. In case of multiple IR/optical counterparts they focus on the brightest. IGR J16426+6536: The observed counterpart is USNO B1.0 1555-0172189 that is found within the 8" XMM-Newton error box. The authors identify this source as a Sey 1.5 at z=0.323. They further discuss the likelihood of the association of this counterpart to the high energy source, and conclude that the fact it is a Sey source renders very likely the association. Additional considerations lead them to estimate a mass of 9e6 solar masses for the central black hole. IGR J18214-1318: They find a reddened continuum possibly indicating a quite large distance for this source. They estimate V=22.2, R=19.3 and I=16.2. Discussing the type of this source based on its X-ray spectral shape, and optical spectrum they conclude that this source is an HMXB. The optical spectra lead them to further classify the companion as a either a B0 V or a O9 I star. Other considerations (such as the variable value of the Nh inferred from the X-rays) argue in favour of a supergiant HMXB. IGR J18308-1232: A chandra observation allowed the position of this source to be refined (to be published). The Chandra error is consistent with USNO-B1.0 0774-0551687. The optical spectrum is typical of either CVs or LMXBs. The X-ray spectrum is however to hard for the source to be an LMXB. The authors obtain V=17.1, R=17.1, I=16.2. Froim this and for a typical CV they estimate a distance d~220 pc IGR J19267+1325: The analysis confirms the CV and magnetic nature of this source, which therefore is an IP. They find V=17.4, R=16.7 and I=15.8. From this and the optical extinction (taken at a different value from previous work) they estimate a distance of ~250 pc IGR J22292+6647: USNO B1;0 1567-0242133 lies inside the Swift error box. The optical spectrum is flat with one strong and broad emission line, which, assuming it is Halpha, leads to the conclusion that the source is a Sey 1 at z=0.113. The authors further discuss some of their results and in particular plot the distribution of INTEGRAL AGN vs their redshift, and show that the 2 AGN identified through their study are amongst the farthest. More details in Butler et al. 2009 arXiV 0903.1302 Romano et al. 2009 ATel 1961 report the detection of a flaring activity in IGRJ17391-3021 detected with Swift from 2009 March 10 at 18:39:55.43. Other observations performed on 2009-03-11 05:52:47 for about 2 ks showed a decrease of the source as seen with the XRT. The detection significance was 4.8 sigma. More details in Romano et al. 2009 ATel 1961 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #322 Feb 20 2009 |
Kotze and collaborators, 2009, accepted in MNRAS
report the long term analysis of the ASM light curves
of IGR J17098-3628, and present a comparison with
those of EXO 0748-676.
They found a quasi-priodic modulation of 163 d only
seen during the active states of the source.
They add that the light curve is not typical of X-ray transient,
and therefore the source is a pseudo-transient.
Although the orbital period, the companion and the type of the compact object are not known in the IGR source, the similarity of its behaviour with that of the EXO source leads Kotze et al. to suggest it is a LMXB, in a relative short (<1d) orbit. They present some discussion on the possible origin of the superorbital period in those two sources. More details in Kotze et al. 2009 arXiV 0902.3385 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #321 Feb 13 2009 |
Romano et al. 2009, accepted in ApJ
describe their recent
observations of the peculiar SFXT IGR J11215-5952. This
SFXT features an unusual 165-day periodic outburst.
Anticipating its apastron passage, the authors observed the source for
32ks with Swift between June and July, 2008. The outburst during this passage,
which reached a luminosity of 10^36 erg/s in the 1--10 keV band, is similar to the
outburst that was monitored during the periastron passage of February, 2007.
The average spectrum can be fit by an absorbed (nH~1e22) power law of photon index 1.
This hard spectrum is consistent with previous Swift observations of the source.
Having followed the source prior to, during, and after this outburst, the authors
conclude after comparisons with previous outbursts, that the orbit is eccentric with
a period of 164.6 days. There is no evidence for a change in column density during
the course of this outburst, nor in comparison with previous outbursts.
They suggest that the outbursts during the periastron phase are due to the compact
accretor crossing equatorial winds of differing density. These winds are in addition to
the spherically-symmetric winds typically found around supergiant stars. Inhomogeneities
(clumps) in the slow, dense equatorial wind could be responsible for the varying
X-ray intensities seen from the source. The steep rise in luminosity and narrow shape
of the outburst can be explained by an equatorial component that is inclined with respect
to the orbital plane. A more recent ToO observation from March, 2008, leads the authors
to exclude a fractional orbital period of 165/2 days.
The authors discuss these results in the context of the geometry of this system and of other SFXTs. For more details of their analysis, please read Romano et al. (accepted in ApJ): arXiV 0902.1985 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #320 Feb 9 2009 |
La Parola et al. 2009, ATel 1929, report the detection
of a new bright flare with Swift from the SFXT IGR J16479-4514
that has recently been seen in activity.
The author mention that this is part of the same outburst that triggered Swift/BAT on January 29. The Swift/XRT light curve obtained from the monitoting of the source shows a large variability, with the source being always detected, which demonstrates that it is still active since January 29. The XRT spectrum has parameters compatible with those obtained during the previous flares. The authors further discuss these observations and mention that in IGR J16479-4514 bright flares spaced by a few days are part of the same outburst. They also suggest that this could be the case also in other SFXTs. More details can be found in La Parola et al. ATel 1929 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #319 Jan 30 2009 |
Romano et al. 2009 ATel 1920 report the detection
of a new outburst of IGR J16479-4514 detected with
Swift/BAT on January 29 at 06:33:07 UT. The time-averaged spectrum from T-419 to T+964 s is well fitted with a simple power-law model with Gamma=2.5. The source was within the XRT fov 819.3s after the BAT trigger. The source has declined from 4 to about 0.5 count/s in the time interval 864-7529 s after the trigger. The XRT spectrum is power law like with Gamma~1.00 modified by absorption with Nh~4.79E+22 cm-2. All these parameters are consistent with those derived during the previous outburst seen about 315 days ago More details in Romano et al. 2009 ATel 1920 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #318 Jan 20 2009 |
Pretorius 2009 accepted in MNRAS
report the results of optical observations of 5 CVs
4 of which are IGRs. These are
IGR J15094-6649, J16167-4957, J16500-3307
and J17195-4100.
Phase resolved spectroscopy allows Pretorius to revealed the orbital period for all four sources at 5.89h, 5.004h, 3.617h and 4.005 h for J15094-6649, J16167-4957, J16500-3307 and J17195-4100 respectively. She also reports the measurements of the spin period of the white dwarf in J15094-6649, J16500-3307 and J17195-4100 to 13.4904, 9.9653 and 18.9925 min respectively, which confirms the IP nature of these three systems. She does not see any modulation in the remaining source, and therefore is not able to confirm its IP nature More details in Pretorius 2009 arXiV 0901.2841 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #317 Jan 19 2009 |
Malizia et al. 2009
accepted in MNRAS report the study of
IGR J16351-5806 using INTEGRAL and XMM.
They first of observe that the broad band spectrum of the source is flat and shows a prominent iron emission line. These two things are indicative of a Compton thick Sey 2. They then present spectral fitting of the spectrum. 3 models can represent the data well:
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| Mail #316 Jan 05 2009 |
Coe et al. 2008 ATel 1882 report the discovery of a new source, IGR J015712-7259.
The source was found in the INTEGRAL Key Project observations of
the SMC and Magellanic Bridge. A follow-up observation with Swift has allowed the authors to refine the X-ray position to RA= 01h 57m 16.4s Dec= -72deg 58' 33" with an error of 3.7 arcsec. This observation and subsequent RXTE ones permitted Coe and collaborators to find a pulsation at 11.6s. An USNO star with R=15.4 is found within the Swift error box. According to the authors all these results suggest this new source is an HMXB in the Magellanic Bridge. More details in Coe et al. 2008, ATel 1882 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Mail #315 Dec 17 2008 |
Tomsick et al. 2009 accepted in ApJ
report the results of XMM-Newton observations of
IGR J16207-5129.
The authors present the results of both a spectral and temporal analysis of the source. The XMM spectrum is reminiscent of those of HMXBs, ie it is well fitted with a hard absorbed power law, with the inclusion of an additional power law to account for a soft excess visible at low energies. The value of Nh obtained with XMM leaves no doubt that the source is an obscured HMXB. The authors also refitted their previous Chandra data with the same model as the one used for the XMM spectrum and also found a value of the absorption in significant excess to the galactic value. Tomsick and collaborators also investigate the possibilty that the short term variability seen in the XMM light curve is due to variation of Nh, and they conclude that this alone cannot be the origin of the source fluctuation of flux. They study the presence of pulsations in this source over a wide range of frequencies, and do not find any pulsation between 0.005 and 88 Hz with a 90% upper limit of 2.3 % RMS. A slightly different treatment of the lowest frequencies lead them to conclude to a non detection of pulsation between 0.000023 and 0.05 Hz with a 90% upper limit of 1.7% The authors further discuss their results in the framework of HMXBs in general and argue about the nature of the compact object. They, in particular, indicate that the lack of pulsation should not be taken as evidence for the compact object being a black hole. Much more details in Tomsick et al. 2009 arXiV 0812.2975 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #314 Nov. 28 2008 |
Rodriguez et al. 2009 accepted in A&A report the results
of Swift observations of 17 IGR sources most of which (13) did not have
an ~arcsec accuracy X-ray position. These sources are: IGR J03184-0014, J03532-6829, J05319-6601, J05346-5759, J09025-6814, J10101-5654, J13000+2529, J13020-6359, J15161-3827, J15479-4529, J16287-5021, J17353-3539, J17476-2253, J18214-1318, J19267+1325, J20286+2544, J23206+643. For 13 sources we find the X-ray counterpart without any ambiguity, In four cases we only find a very slight excess in the IBIS error box. For all sources, we provide the X-ray position with ~arcsec accuracy, identify possible infrared and optical counterparts (when found), give the magnitudes in those bands and in the optical and UV as seen with the SwiftUVOT telescope when observations are available. We also make use of the spectral results in trying to identify the nature of those sources. Our main results can be summarised as follows: We confirm that:
In the cases several X-ray counterparts were detected, the spectral analysis of each of those sources allowed us to suggest that
Of the six remaining source:
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| Mail #313 Nov. 27 2008 |
Masetti et al. 2008 accepted in A&A report the results
of optical spectroscopy of 20 sources 18 of which
are IGRs. These sources are: IGR J00333+6122, J02466-4222, J02524-0829, J05270-6631 J08390-4833, J09025-6814, J09253+6929, J10147-6354, J11098-6457, J11435-6109, J12415-5750, J16426+6536, J17404-3655, J18173-2509, J18249-3243, J18308-1232, J19267+1325, J21347+4737 For all sources they provide the key parameters that allow them to identify the nature of the sources, give the spectral type of the counterpart for the galactic sources, give an estimate of the distance, and for the Sey 1 they give the mass of the BH. The identifications are as follows:
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| Mail #312 Nov. 25 2008 |
Remillard & Levine, 2008 ATel 1853 report on the analysis
of a mission long ASM light curve of IGR J17062-6143.
Binning the flux measurements to intervals of one week, they could obtain
a light curve that shows that the source is a long-term, faint transient, whose
current outburst began in late 2005 or early 2006.
Remillard and Levine add that the source was weakly detected at 3.1 mCrab over the period 53600 to 53800, and then rose to 5.1 mCrab between 53800 and 54540. It further increase to a levele of 6.3 mCrab between 54540 and the present day (54794). According to these authors, and based on the value of the hardness ratio (HR2 = 1.3) from the last interval, this source is a soft X-ray transient rather than a classical accretion-powered pulsar More details in Remillard and Levine 2008 ATel 1853 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #311 Nov. 19 2008 |
Zurita Heras & Walter 2008 , accepted in A&A
present a study of AX J1845.0-0433=IGR J18450-0435 performed with
INTEGRAL and XMM-Newton.
They confirm the O9.5I supergiant companion with the most-accurate X-ray
position of R.A. (2000) =18h45m01s.4 and Dec. = -04deg33'57''.7 (uncertainty 2'').
Both observatories detect the quiescent luminosity of the source with
L(0.2-100 keV) ~ 1e35 erg/s that implies a binary separation of ~3 Rstar, higher
than in other known supergiant HMXB.
XMM-Newton detected two bright and short flares that reached L~1e36 erg/s, implying
a maximum variability factors of 50 on time scale of a few hundreds of seconds. The
broad-band high-energy spectrum is typical of wind-fed accreting pulsars
(NH=(2.6+/-0.2)e22 cm-2, Gamma=(0.7-0.9)+/-0.1 and Ecut=16+/-3 keV). An excess at
low energies is also observed and fitted with a black body (kT=0.18+/-0.05 keV).
Optically-thin and highly-ionised iron (Fe XVIII-XIX) located in the vicinity of the supergiant
star is detected during the quiescence phase. The spectral shape of the X-ray continuum is
constant. The flare characteristics in contrast to the persistent quiescent emission suggest
that massive clumps are formed within the stellar wind of the supergiant companion.
More details in Zurita Heras & Walter 2008,
arXiV 0811.0983
I warmly thank J. Zurita Heras, for having written this summary. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #310 Nov. 18 2008 |
Paizis et al 2008 accepted in PASJ,
present the best available broad-band X-ray spectrum
of the BH LMXB IGR J17497-2821, as observed by Suzaku eight days after its
discovery (September 2006). The source is very bright, with L(1-300 keV) = 2 10^37 erg/sec at 8 kpc, and has a very hard spectrum. A fit with a simple phenomenological model gave a constrained high energy cut-off around 150 keV, naturally driving the choice for the model used to interpret the data in a physical scenario (diskbb+compps): soft seed photons coming from the disc are thermally up-scattered by a hot and patchy corona. A very mild reflection component is seen for the first time in the spectrum. Though not conclusive, there is a hint of spectral hardening about 10 days after the peak outburst with the source remaining in its Low Hard State all along the outburst. More details in Paizis et al. 2008 arXiV 0811.2663 I warmly thank A. Paizis for having written this summary Landi et al. 2008 accepted in A&A report the identification of 3 IGRs as (possible) AGN. The sources are IGR J18249-3243, J19443+2117 and J22292+6647. For each of the sources, the authors report the refined position obtained with Swift/XRT and joint XRT - INTEGRAL/IBIS spectral analysis, and the results of their search for radio, IR Optical and UV counterparts. IGR J18249-3243 is a complex radio source with at least 3 components reported in the NVSS catalogue. It is reported as an asymmetric double in NED. They also report the presence of a USNO B1.0 (R=14.6-14.8) and 2MASS (J=13.456, H=13.007, K=12.675) source. It is also detected in the UVOT with UW2=17.53. The source is classified as an AGN. Further Optical spectroscopy (in a submitted paper) confirms this interpretation and provides z=0.355 IGR J19443+2117: Only one component is reported in NVSS, while a J>14.53 H>13.36 and K=13.980 2MASS object is found oin the XRT error box. This object is not detected in the optical and UV bands. TheX-ray spectral analysis may indicate some intrinsic absorption. The authors tentatively classify this source as a radio quiet AGN, although they remark that this classification remains uncertain. IGR J22292+6647: This source also has a counterpart in the NVSS catalogue. It is also detected in 2MASS with J=16.602, H=15.707 and K=14.683. The author also performed optical observations and detected a counterpart with R=19.2. Several X-ray observations also allowed Landi et al. to remark some variability in this source. However it seems that only the luminosity varies and not the spectral shape. The authors conclude that this object is an AGN, probably a border line between radio quiet and radio loud More details in Landi et al. 2009 arXiV 0811.2318 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #309 Nov. 17 2008 |
Ricci and collaborators report the results of
Swift and INTEGRAL observations of IGR J17062-6143
The source is clearly detected by Swift and has also been named Swift J1706.6-6146. The Swift/XRT position is RA=256.5690 deg DEC=-61.7119 deg (+-3.5 arcsec) The 0.3-7 keV spectrum can be represented by an absorbed power law, with NH = 1.7e21 cm-2 and a photon index 1.86. The hard X-ray spectrum can be modeled by a single power law with a photon index 2.8, or by a black body with kT ~ 7keV. A single object is detected with Swift/UVOT within the XRT error circle. It lies at RA=17 06 16.3, DEC=-61 42 40.5 (+-0.3 arcsec). It is therefore at 3 arcsec from the XRT position. This object has U=18.4 mag and UVW2=18.1 mag. No source is detectable at this position in the 2MASS and NVSS data. More details in Ricci et al. 2008 ATel 1840 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #308 Oct. 25 2008 |
Campana et al. 2008 accepted for publication in ApJ letters
report the results of XMM observation of the accreting
millisecond X-ray pulsar IGR J00291+5934 in quiescence.
They, for the first time, report thermal emission from an AMXP while in quiescence. This thermal emission is either modeled with a neutron star atmosphere (64 eV) or a black body (110 eV). These authors further discuss this finding, and in light with the fluence of the source during outbursts, remark that this thermal emission is compatible with cooling of the neutron star surface. By comparing the parameters of this source with other AMXP, they conclude that the neutron star in IGR J00291+5934 has a Mass smaller than 1.6 sol Masses More details in Campana et al. arXiV 0810.4804 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #307 Oct. 25 2008 |
First, and although the source is not really a genuine new INTEGRAL
source (it was discovered by HEAO) the outburst of H1743-322/IGR J17464-3213
is still ongoing and Belloni et al. 2008, Prat et al. 2008 Atels 1804 and 1808
both mention a transition to a softer state than the one it has been seen
until now (during this outburst). More details in ATels 1804 and ATel 1808 Cadolle Bel et al. 2008 ATel 1810 analyse data of the field around SAX J1753.5-2349.br> The authors first re analysed archival data of this field to try and investigate the nature of IGR J17536-2339. They mention that using the latest version of the software, they do not detect the source in the same data from which it had been discovered. Cadolle Bel and collaborators conclude that GR J17536-2339 is probably a spurious source. They also add that the recently reported new hard X-ray transient IGR J17375-3022 is not detected anymore in the Oct 17-19 observations. They derive a 18-40 keV upper limit of ~3 mCrab, and suggest the source has returned to quiescence. More details in Cadolle Bel et al. ATel 1810 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #306 Oct. 23 2008 |
Parisi et al. 2008, ATel 1800 report the results of
optical spectroscopy of XMMSL1 J164303.7+653253
the possible counterpart to IGR J16426+6536.
The optical counterpart is USNO-A2.0 1500-06133361
sitting at RA = 16 43 04.07, Dec = +65 32 50.9 that has R ~ 18.9 We found that the optical spectrum of the source shows a blue continuum with superimposed several redshifted emission features, among which Hbeta, Hgamma, Hdelta, and Hepsilon Balmer lines, as well as narrow [OII] and [OIII] lines. Using the narrow emission features, we determine a redshift z=0.323+-0.001 for the source. The authors conclude that XMMLS1 J164303.7+653253 is a Seyfert 1 AGN. The authors further discuss the possible association with the IBIS source and conclude that they are confident about the association of the XMM source and the INTEGRAL one. Hence IGR J16426+6536 is a Sey 1 AGN More details in Parisi et al. 2008 ATel 1800 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #305 Oct. 18 2008 |
Galloway et al. 2008, ATel 1786 give a short summary
of the recent activity of the accreting ms pulsar IGR J00291+5934.
The source has undergone a double outburst as seen with RXTE at X-ray energies, and in optical. The source reached its first maximum between Aug 13 and 15, at a 2.5-25 level of 6.3e-10 erg/cm^2/s. It then decreased to ~7e-11 erg/cm^2/s by 21 Aug, and stayed at this low luminosity level until mid-Sept. Similarly, Galloway et al. remark that the optical counterpart had also faded significantly by Aug 24. Rebrightening in the optical and X-ray bands on Sep 18 was reported. On Sept. 21 the 2.5-25 keV flux had increased to 2.3e-10 erg/cm^2/s, and pulsations were detected once more. The 2nd peak had a flux of 5e-10 erg/cm^2/s and occured between Sep 24 and 26. Galloway et al. add t he outburst interval seems to have been steadily increasing with time. More details in Galloway et al. 2008 ATel 1786 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #304 Oct. 16 2008 |
Beckmann et al. 2008, ATel 1783, report the results
of a Swift foolow up observation of IGR J17375-3022.
A single bright source is detected in the IBIS error box at RA=17h 37m 33.86s DEC= -30deg 23' 15.4" (+-3.5"). The XRT spectrum can be represented by an absorbed power law model with Gamma=2.3, and an intrinsic Nh=1.6 e22 cm-2 (with a Galactic Nh =1.2e22 cm-2). Beckmann and co-workers remark that other models such as a black body or a compTT give a significantly worse fit result to the data. Mored details in Beckmann et al. 2008 ATel 1783 Burenin et al. 2008 accepted in Astro. Letters, report the results of optical spectroscopy of the counterpart to IGR J18257-0707. The magnitude of the optical counterpart is R~20.4, and although it is quite faint, their optical spectroscopic observation allowed them to identify the presence of Halpha at z=0.037. The authors therefore classify this object as a nearby Sey 1 Galaxy. Burenin et al. further discuss their findings and mention in particular that their results are compatible with low intrinsic absorption of this source More details in Burenin et al. 2008 arXiV 0810.2512 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #303 Oct. 14 2008 |
Ricci et al. 2008, ATel 1781, report the discovery of
a possible new source IGR J17375-3022 with IBIS/ISGRI.
The INTEGRAL position given by Ricci et al. is RA= 17h 37m 34.7s Dec=-30deg 22' 54.1" (+-2.2 arcmin) The source is detected at an average flux of 10 mCrab in the 20-40 keV range. and 7 mCrab in the 40-80 keV. It is not detected by SPI, or JEM-X. Itis not detected in the previous and the following revolution in any of the INTEGRAL instruments. The source is detected in ISGRI up to 150 keV and the spectrum can be fitted by a single power law with a photon index of Gamma = 2.0. Assuming that the source is at a distance similar to the Galactic centre, the spectrum leads to a 20-150 keV luminosity = 1.5e+36 erg/sec. More details in Ricci et al. 2008 ATel 1781 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #302 Oct. 14 2008 |
Landi et al. 2008, accpeted in MNRAS,
report the results of INTEGRAL observations
of 22 CVs, of which 10 are purely IGR sources.
They also report Swift analysis of 11 of those sources (this sub sample
includes 7 IGRs).
The IGRs are: IGR J00234+6141, IGR J06253+7334, IGR J14536Ð5522 IGR J15094Ð6649, IGR J15479Ð4529, IGR J16167Ð4957, IGR J16500Ð3307 IGR J17195Ð4100, IGR J17303Ð0601, IGR J21335+5105 For all sources they provide the type of the CV (DN, IP, or Polar), and the spectral parameters obtained from the fits to the INTEGRAL data with either a power law or a bremsstrahlung. Landi et al. remark that, while fitting together all sources, a bremsstrahlung provides a better representation with an average kT=22 keV. They also report the individual Swift+INTEGRAL spectral analysis of the source observed with both satellites. The sources are well fitted with a model of (partially) absorbed black body + bremsstrahlung. Some need additional components such as an iron line or a thermal emitting plasma. The authors further discuss their results in the context of the physics of CVs. More details (especially on individuals sources) can be found in Landi et al. 2008 arXiV 0810.1844 Bikmaev et al., Astr. Letters, 2008, 34, 653, report the optical identification of 4 IGRs. IGR J20216+4359: Before observing the source in optical, the authors first mention the existence of a soft X-ray counterpart of the IGR as seen with ASCA. The refined position is : RA=20h21m 48.1s Dec=+44deg 00' 32" (+-20"), and the spectrum is strongly absorbed (Nh=13e22 cm-2). They then found an AGN in their optical data , lying in the ASCA error box. The optical spectrum leads to the classification of this AGN as a Sey 2 object at z=0.017 IGR J21343+4738: The authors confirm that the source is a probable HMXB hosting a B star IGR J23206+6431: The authors provides images and results of their analysis that led them to classify it as a Sey 1 at z=0.07173 IGR J23523+5844: The author further confirm that this source is a Sey 2. They refine the redshift to z=0.1620. They remark that the OIII line emission is spatially shifted from the continuum emission, and further discuss this issue. More details can be found in Bikmaev et al. 2008, arXiV 0810.2018 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #301 Oct. 13 2008 |
Kuiper et al. 2008 ATel 1774, report the discovery of
a new source in deep mosaic of the Norma region.
IGR J16293-4603 is located at: RA=16h 29m 12.87s DEC = -46deg 02' 50.9" (+-0.6 arcsec) as obtained in a Chandra follow up observation. The time averaged INTEGRAL spectrum was fitted with a power law with Gamma=1.85 and a 20-70 keV flux of 1.2e-11 erg/cm2/s. The 0.3-7 keV spectrum was fitted with an absorbed power law and yielded Gamma=1.0 and Nh=0.7 e22 cm-2. The authors obtained optical observations of the field and found an extended object at the Chandra position. This object is consistent with being at least three unresolved point-like sources. Kuiper and co-workers further discuss their indings and conclude that the data is consistent with the source being an AGN or a peculiar galactic X-ray binary. More details in Kuiper et al. 2008 ATel 1774 Ricci et al. 2008, ATel 1779 report about recent INTEGRAL observations of the ongoing outburst of H1743-322/IGR J17464-3213. The observing periods cover 2008-10-10T05:19 to 2008-10-10T11:19 and from 2008-10-10T21:34 to 2008-10-11T21:57. Ricci et al. mention that the source showed little variability in the 20-40 keV band around a mean flux of 170 mCrab. They therefore accumulated averaged spectra from the whole data set. The combined JEM-X, IBIS, and SPI spectrum is well fitted by an absorbed comptt with Nh = 1.8 e22 cm2, kT_e = 39keV, and tau = 1.2 Yamaoka et al. 2008 ATel 1780, report the results of RXTE observations of the same source. They fitted the PCA and HEXTE spectra in the 3-200 keV range with a power-law (Gamma in the range 1.34-1.44), with a high energy cutoff (83-94 keV), modified by Galactic absorption and smeared edge at 7.11 keV due to cold iron. Yamaoka et al. remark that while the PCA 3-20 keV flux gradually increases over the various observations, the HEXTE 20-100 keV decreases in the same time. They interpret this as evidence of a transition into the hard intermediate state. They also detect a low-frequency QPO with frequency increasing from 0.3 to 0.6 Hz (from Oct 3 to 11) More details in Ricci et al. 2008 ATel 1779 and Yamaoka et al. 2008 ATel 1780 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #300 Oct. 9 2008 |
Revnivtsev et al. 2008
accepted in Astronomy Letters,
report the results of optical observations of IGR J08390-4833.
Through spectroscopic analysis they first conclude that the source as a Galactic one, and further idenitfy it as a Cataclysmic Variable. This object indeed shows strong Balmer emission lines at z=0, and a shape that is consistent with other CVs. The authors remark the presence of a nebular emission not too far from the source. They study the possible origin of this emission and mention that there is no clear association of this nebular feature and the IGR source. The optical light curve of the source does not show any evidence for periodic variations. More details can be found in Romano et al. 2008, arXiV 0810.1434 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #299 Oct. 8 2008 |
Romano et al. 2008 accepted in MNRAS report the results of
Swift observations of the SFXT IGR J08408-4503 during two
outbursts.
They first report that although their data of the first (2006) outburst do not allow them to see significant (>3sig) variations of the hardness ratio, the source gets softer with increasing luminosity during the second outburst (2008). The 2008 outburst is composed of multiple flares each exceding 1e36erg/s They then present spectral analysis of the XRT+BAT data. The two outburst show significantly different spectral parameters. Time resolved spectral analysis is also presented and the authors show that, during the 2008 outburst, there is a definite evolution of the absorbing column density along the outburst. The authors discuss their findings and mention that:
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| Mail #298 Oct. 7 2008 |
Following the reactivation of H1743-322/IGR J17464-3213 in hard
X-rays, Corbel et al. 2008 ATel 1766, report the results of their
radio observation with ATCA.
The source was observed on 2008 October, 5 and apparently detected with preliminary flux densities of 2.30 mJy at 4.8GHz and 1.80 mJy at 8.6 GHz, which gives a spectral index of -0.42. The negative spectral index of the radio emission indicates optically thin synchrotron emission from H1743-322. Corbel et al. add that although this index may be surprising for a hard state source, H1743 may actually be undergoing a state transition to a softer state since it becomes visible in the RXTE/ASM band, and seem to have reached a plateau as seen in hard X-rays. More details in Corbel et al. 2008 ATel 1766 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #297 Sep 27 2008 |
Prat, Rodriguez & Cadolle Bel 2008, ATel 1745 report
the results of more INTEGRAL observations of H1743-322/IGR J17464-3213.
INTEGRAL Galactic centre Key Project observations
performed between Sep 23 12:36 and 2008 Sep 25 05:09
confirm that the source has entered a new outburst.
The authors performed spectral analysis of the IBIS/ISGRI data
and because of evolution of the flux of the source they
separated the observation in 2 intervals.
During the first one the source is detected with fluxes of ~26 mCrab (20-40 keV),
36 mCrab (40-80 keV), and 50 mCrab (80-150keV), and the IBIS/ISGRI spectrum
can be well fitted with a cutoff with a photon index of 1.3 and a cutoff energy Ecut=151
(-66, +54) keV.
During the second interval, the source is detected with fluxes
of ~47 mCrab (20-40 keV), 66 mCrab (40-80 keV), 89 mCrab (80-150 keV),
The spectrum is well fitted by a simple power law with a photon index 1.64.
A cutoff is not required by the fit.
Prat et al. conclude that the source is in a Hard State in a very early phase of its outburst. More details can be found in Prat et al. 2008 ATel 1745 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #296 Sep 26 2008 |
Kuulkers et al. 2008, ATel 1739 report renewed
activity of the black hole binary H1743-322/IGR J17464-3213.
The source is clearly detected in their Galactic BUlge monitoring
on 2008 Sep 23 08:51-12:34 with both JEM-X and IBIS/ISGRI.
The source was not detected in previous observations, which indicates that it is entering a new episode of outburst. More details in Kuulkers et al. 2008 ATel 1739 Rahoui and Chaty 2008 accepted in A&A report the results of optical and near infrared observations of IGR J18483-0311. Through the spectroscopic analysis of their data and the identifications of several emission and absorption line they can classify the companion star as a B0.5 Ia supergiant. This source is therefore not a Be X-ray binary as had been suggested before. They then fitted the SED of the star and obtained a best fitted temperature of 24 600 K and estimate a distance to the source of 3-4 kpc. Rahoui and Chaty discuss their findings and comparing to previous analysis conclude that the system is a new Supergiant Fast X-ray Transient, although with peculiar characteristics compared to other such sources, which makes it a intermediate SFXT (longer duration of flares, lower Lmax/Lmin ratio...). The authors conclude that IGR J18483-0311 probably has a small and eccentric orbit. More details in Rahoui and Chaty 2008 arXiV 0809.4415 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #295 Sep 23 2008 |
Bozo et al. 2008 accepted in MNRAS report
the results of a long XMM observation of the SFXT
IGR J16479-4514.
They triggered their observation just after a bright falre observed with Swift. The XMM observation is divided in two parts, one having a count rate higher than the other by a factor of ~50. This bright phase is most probably the tail of the bright burst. Bozzo et al. performed X-ray spectroscopic analysis of these two phases and show that the faint phase is probably due to obscuration of the source of X-rays. They discuss several possibilities for this behaviour and favour an X-ray eclipse as the origin. In addition these authors report the presence of an extended (tens of arcsec) dust scattering halo. More details, and a full discussion on the duration of the eclipse can be found in Bozzo et al. 2008 arXiV 0809.3642 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #294 Sep 22 2008 |
Mangano et al. 2008 ATel 1727
report the results of Swift observations of IGR J08408-4503.
The source triggered Swift/BAT on 2008-09-21 at 07:55:08 UT. The light curve is consistent with being constant until T+730s. The spectrum in the same time interval is well represented by a powerlaw with an exponential cutoff, with Gamma=1.3 , and a cut off energy of 22.7 keV. The authors note that a simple power law gives a photon index of 2.87 (and an acceptable fit too) The Swift/XRT light curve shows a bright flarewith a flat top phase that lasts about 1 ks. 5 ks later, the source had already decayed by a factor of 40 in count rate. The XRT spectrum of the first orbit (bright flare 1ks ) is well fitted by an absorbed powerlaw with a Gamma=0.85 and Nh=2.9E+21 cm-2 The XRT of the subsequent time interval can be fitted with an absorbed powerlaw with Gamma=0.8 and Nh=3.7 E+21 cm-2. More details can be found in Mangano et al. 2008 ATel 1727 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #293 Sep 20 2008 |
Lewis et al. 2008 ATel 1726 report that the accreting
ms pulsar IGR J00291+5934 is re-brigthening in
optical and X-rays.
Renewed activity of the source was first seen in optical on 18th September with a detection at i' = 17.38 , which is ~0.2 mag fainter than the outburst peak on 15th August. They then obtained a Swift pointing on the source which confirmed the re-brightening of IGR J00291+5934. The X-ray flux is a factor of ~2 fainter than that of the peak in august. More details can be found in Lewis et al. 2008 ATel 1726 while the optical light curve is available at http://staff.science.uva.nl/~davidr/faulkes/IGRJ0029.html | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #292 Sep 17 2008 |
Capitanio et al. 2008 accepted in ApJ report multiwavelengths
observations of two IGR black hole candidates IGR J17091-3624
and J17098-3628.
IGR J17098-3628: This source has been regularly detected by INTEGRAL and RXTE over the period 2005-2007. The source showed slight variations of the flux, while the spectra show that the soft component, a disc black body, remained essentially the same over the entire 2.5 years period, the hard tail fell below the detection threshold of IBIS 3 months after the begining of the source outburst. According to Capitanio et al. the source remained in a soft state over these 2.5 years. They further confirm all previously suggested associations (radio counterpart, etc). IGR J17091-3624: This source has first been (un)seen in quiescence with an upper limit on the luminosity of L< 7e32 erg/s. This is used by the authors to argue that the source most probably hosts a black hole. They then caught the begining of a new outburst with Swift. The swift refined position (annonced through an ATel) allows them to refute the previously suggested radio counterpart for this source. Re analysing VLA data they find a new radio counterpart at a position consistent with that of the Swift source. The radio spectrum is inverted (ie self absorbed) which is typical of the hard states of black hole. The swift spectrum also indicates a hard spectral state The source then softens, and a black body component needs to be added to represent the subsequent spectra. More details and all spectral parameters can be found in Capitanio et al. 2008 arXiV 0809.2180 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #291 Sep 13 2008 |
Krimm et al. 2008 ATel 1714 report the results of Swift observations
of IGR J17379-3747. The source was detected with the XRT
and this allowed them to improve the X-ray position of the source
to RA=17h 37m 58.81s Dec= -37d 46m 19.6s +-1.4" (at 90% confidence) The XRT spectrum can be fitted by an absorbed power law spectrum with Nh = 8.1 e21 cm-2, and Gamma= 1.78 Krimm et al. mention some variability as seen in the XRT light curve while the time averaged rate in the BAT remains steady at about 13 mcrab. More details in Krimm et al. 2008 ATel 1714 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #290 Sep 11 2008 |
Further to the association of IGR J17379-3747 with and XTE source
Shaw et al. 2008 ATel 1711 report that this source was also detected
by INTEGRAL/ISGRI during a Galactic Bulge Monitoring observation
starting on 2008-09-05 and lasting 12 ksec.
The 18-40 keV flux was 19 mCrab a factor of 2 higher
than the 15-50 keV flux reported by BAT.
Shaw et al., also report an improve INTEGRAL position for this source. Then using the positions given by the three satellites (RXTE, Swift and INTEGRAL), refine the position of the source to RA, Dec= 264.509 -37.7513 (J2000) +- 1.8 arcmin. More details in Shaw et al. 2008 ATel 1711 Pacciani et al. 2008 ATel 1713, report an observation of IGR J16318-4848 caught in a bright state with the super Agile detector onboard Agile. The source was seen on Sept 10 at a 20-60 keV flux (of 300 mCrab) 10 times higher than its average flux reported in the 3rd IBIS catalogue. More details in Pacciani et al. 2008 ATel 1713 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #289 Sep 10 2008 |
Markwardt et al. 2008, ATel 1709 report the detection of
a new outburst from a source named XTE J1737-376.
This source is also detected by the BAT onboard Swift,
at a position consistent with an INTEGRAL source
reported in the 3rd IBIS catalogue.
Given the positional consistency of the BAT and INTGRAL source
and the BAT and XTE source, Markwardt and collaborators suggest
that XTE J1737-376 is IGR J17379-3747, which therefore is
a transient source.
More details in Markwardt et al. 2008
ATel 1709
the XTE light curve can be found
here
(courtesy C. Markwardt)
Parisi et al. 2008 ATel 1710 report the results of
optical spectroscopy of candidates counterparts
of XMMLS1 J183049.6-123218= IGR J18308-1232.
They mention in particular that the spectrum of
USNO-A2.0 0750-13371563
(at RA = 18 30 49.88, DEC = -12 32 18.7 with R ~ 17.0)
shows a red continuum, possibly absorbed by the Galactic dust
along the line of sight, with several Balmer, HeI and HeII narrow
emission lines at z ~0. The EW of the Halpha emission
is ~ 22 Angstrom.
Parisi et al. say that this spectrum resembles that of a CV and, given the relative strength of the HeII emission line, they suggest the presence of a magnetic white dwarf in this system. They therefore conclude that USNO-A2.0 0750-13371563 is the optical counterpart of IGR J18308-1232, and as such is a Cataclysmic Variable, possibly hosting a magnetic white dwarf. More details in Parisi et al. 2008 ATel 1710 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #288 Sep 4 2008 |
Romano et al. 2008, ATel 1697, report a bright flaring
activity of the SFXT IGR J17544-2619, seen with Swift
in observations starting on Sept 4, 2008.
This follows observation of intense activity seen with INTEGRAL and reported ealier. The IBIS 18-40 keV peak is ~50 mCrab The XRT light curve shows a peak exceeding 20 counts/s, which is brighter than the March 31, flare. The XRT spectrum can be fitted with an absorbed power law with Gamma=1.3 and NH=1.8E+22 cm-2. The average unabs. 2-10 keV flux is ~8E-10 erg/cm2/s. Fainter X-ray emission is well represented by an absorbed power law with NH=1.4E22 cm-2, Gamma=0.8 and an average unabs. 2-10 keV flux of ~2E-10 erg/cm2/s . More details in Romano et al. 2008 ATel 1697 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #287 Sep 2 2008 |
Molina et al. 2008,
accepted for publication in MNRAS
report a broad band spectral analysis of 8 radio loud
Sey 1 AGN, two of which (IGR J13109-5552 and
J21247+5058) are IGRs.
The analysis of this two sources is included in a broader context of study of type 1 AGN in general, but individual spectral analysis of each of the sources of their sample is presented. In particular, the spectrum of IGR J13109-5552 is well fitted by an absorbed power law with Nh compatible with the value of the absorption on the line of sight and Gamma=1.70. A cut off power law provides a 83% improvement over the simple power law, with a cut off energy >58 keV. For IGR J21247+5058 the spectral analysis shows evidence for a slightly more complicated model. As mention in previous analysis the source spectrum shows complex absorption by two layers of absorbing material partially covering the central source of X-rays. A power law with a cut-off, or a power law + reflection (plus an iron line in all cases) fit the data well. In both cases the values of the absorption and covering factors are compatible: Nh=0.8e22 cm-2, f~0.9 and Nh=8.2, f~0.3. In the first model the cut-off energy is 80 keV, while in the second the reflection factor R=0.93, with a "flat" power law photon index. The authors further discuss all their results and compare the X-ray properties of this sample to that of radio quiet Sey 1 AGN. They in particular mention thaat the complex absorption is present in all type of Sey 1 AGN independently of their radio activity. More details can be found in Molina et al. 2008 arXiV 0809.0255 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #286 August 29 2008 |
Markwardt 2008, ATel 1686 reports that the recently 120s XTE
pulsar and the IGR source IGR J18246-1425 are the same.
He obtained Swift observation of almost the entire XTE error circle
and detected only one source which is consistent with being
IGR J18246-1425.
He refines the position to RA = 276.0990, Dec=-14.4154 +-4.3" Markwardt also detects the 120s pulsation in the Swift data which further confirms that the XTE and IGR sources are the same More details in Markwardt 2008, ATel 1686 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #285 August 28 2008 |
Chen et al. 2008, accepted in PASJ analyse RXTE/ASM
and INTEGRAL of IGR J17098-3628. They first produce and explore long term (since 1996) ASM and (since 2002) INTEGRAL light curves and identify the periods of activity of the source. They then focus on a period during which the source underwent a hard outburst (March 2005). They first remark that the Soft X-rays lag the hard ones by about 2 days, ie the hard peak occurs before the soft one. They then give an ISGRI spectral analysis of three particular intervals of this outburst, and report that a cut-off pl gives a slightly better representation of the spectra. The joint JEM-X ISGRI spectrum of the decaying phase is well modeled with a broken power law. The authors discuss their results and further confirm that the source is a probable Black hole in a LMXB More details in Chen et al. 2008 arXiV 0808.2359 Sidoli et al. 2008 accepted in ApJ report some results from their ongoing Swift monitoring of 4 SFXTs. Here they focus on analysis of 1 flare from IGR J17544-2619 and one from XTE J1739-302/IGRJ17391-3021. Thanks to Swift broad band coverage they could provide 0.3-60 keV spectral analysis of these two events for the first time. They remark that the two objects, although being considered as the prototypes of SFXTs, have different properties during the flares. IGR J17544-2619: the spectrum of this source is hard (Gamma=0.75) and not so absorbed (Nh=1.1e22 cm-2). Compared to the out-of-outburst periods, the spectrum is much harder but shows a similar absorption. The broad band spectrum is well represented by a Comptonization model with a plasma temperature of 4 keV and an otpical depth of 19. IGR J17391-3021: the spectrum of this source is softer (Gamma=1.5) and shows a high level of absorption (Nh=13e22 cm-2). Compared to the out-of-outburst periods the continuum has a similar shape, but the absorption is significantly higher. Here the broad band spectrum can be described by a soft power law with no evidence for a cut-off. Sidoli et al. 2008 discuss these findings and mention that the spectral characteristics of these sources are typical of accreting X-ray pulsars in binaries. The also discuss their results in the context of models for the emission of X-rays in SFXTs, and add, in particular, that the values of the magnetic fields for these 2 sources, although not directly measured, seem to be incompatible with the model of magnetars recently suggested to explain the behaviour of SFXTs. More details in Sidoli et al. 2008 arXiV 0808.3085 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #284 August 27 2008 |
Tomsick et al. 2008 ATel 1649 report the results of Chandra observations of
two IGRs: IGR J16287-5021 and IGR J19267+1325.
For both they give a refined position, the results of the
Chandra spectral analysis, and the presence or not of
counterparts at other wavelengths.
IGR J16287-5021: is located at R.A. =16h 28m 26s.85 Decl. = -50d 22' 39".6 (+-0".64) The 0.3-10 keV energy spectrum is reasonably well-described by a power-law with little to moderate interstellar absorption and a very hard photon index of Gamma = -0.9. They derive a 90% confidence upper limit of N_H < 1.5 E22 cm-2. They do not find any counterparts in the 2MASS, USNO, or DENIS optical and IR source catalogs. IGR J19267+1325: As mentioned earlier (from swift obs.) no X-ray source is found within the IBIS error, but a bright source can be seen 4.8' away from the INTEGRAL position (consistent with 1RXS J192626.8+132153). The source lies at R.A. = 19h 26m 26s.98 Decl. = +13d 22' 05".1 (+- 0".64) The 0.3-10 keV energy spectrum is well-described by a power-law with N_H = 2.1 E21 cm-2 and Gamma = 0.68 They report USNO-B1.0 and 2MASS counterparts with B = 17.7, R = 16.0 , I= 15.1 , J = 14.94 , H = 14.46 , and Ks = 14.10. The low level of extinction for a source in the Galactic Plane likely indicates that IGR J19267+1325 is a relatively nearby Galactic source Further to that Steeghs et al. ATel 1653 report the results of optical observations of IGR J19267+1325. They report a good match of a source in the IPHAS frames and the Chandra position for the IGR source. The authors add that there is modest variability in the r', i', and H-alpha band. The source has r'=17.70, i'=16.74 and significant H-alpha excess with (r' - H-alpha) = 1.1-1.2 mag. They performed optical spectroscopy of this source and report the presence of strong and broad lines from the Balmer and Paschen series as well as HeI and HeII in emission. The EW of the H-alpha emission line is ~120 A. Steeghs et al. conclude that this spectrum is typical of a cataclysmic variable and the presence of significant HeII emission at a strength comparable to the higher Balmer lines is suggestive of a CV containing a magnetic white dwarf. Evans et al. ATel 1669 further confirms the IP nature of this source using data from Swift. They find strong evidence for a pulsation at 938.6 s with an amplitude of 25%. This is typical of a white dwarf of the IP type. They also report the presence of possible other periods. One of which they associate with the orbital period of the system (4.58 hours). They also report the presence of the first pulsation in the UVOT data. More details in Tomsick et al. 2008 ATel 1649 Steeghs et al. 2008 ATel 1653 Evans et al. 2008 ATel 1669 Altamiraino et al. ATel 1651 report the results of RXTE monitoring of IGR J17473-2721. IGR J17473-2721 reached a maximum unabsorbed flux of ~1.30E-8 ergs cm-2 s-1 (2-10 keV, with nH=3.8e22cm-2) on June 22nd, and has been steadily decreasing since. It switched from hard to soft state and back to hard state. During the soft state, 6 observations show a kHz QPO at frequency up to ~900 Hz, reaching up to 8% rms. These behaviours are typical of neutron star atoll sources. Altamiraino et al. report the detection of 16 type-I X-ray bursts. Two of them exhibited photospheric radius expansion, reaching bolometric fluxes of 9.5e-8 erg/cm2/s. This corresponds to a distance to the source between 4.9-5.7 kpc. More details in Altamiraino et al. 2008 ATel 1651 Romano et al. ATel 1659 report the occurrence of a new outburst of XTEJ1739-302/IGRJ17391-3021 seen with Swift. The BAT triggered twice on 2008-08-13 23:49:17 UT and 2008-08-14 00:12:53 UT. The swift BAT and XRT spectral analysis showed consistent parameters with those obtained during the previous outburst of this source More details in Romano et al. 2008 ATel 1659 Chakrabarty et al. ATel 1660 report the detection of a new outburst of the ms pulsars IGR J00291+5934 detected with RXTE. The source was detected in a RXTE observation done on August 13 while it was not detected in another one performed on August 10 Further to that Markwardt and Swank ATel 1664 confirmed the renewed activity of the same source as seen with Swift. The authors report that the swwift flux is rather compatible with that of PCA although the nearby IP V709 Cas may contribute significantly to the PCA observation. Torres et al. ATel 1665 add that the optical counterpart to IGR 00291+5934 has brightened to r'=18.07 and i'= 17.75 which is more than 4 magnitudes than the quiescent ones, and comparable to the values obtained during the previous outburst. In addition Russel et al. Atel 1666 report the result of their optical monitoring of the source. They also deteted the source at 1 micron. They confirm the brightening of the source in optical and mention that this is contemporaneous to the X-ray brightening. The authors mention an IR excess in the dereddened magnitudes, which they mention as a possible signature of a jet. Linares et al. ATel 1667 however do not detect any radio activity with the WSRT at 4.9 GHz. The 3-sig upper limit is 160 microJy. They add that the simultaneous Swift observation leads to a 2-10 keV flux of 2.2E-10 erg/s/cm2 which is lower than the flux at which radio had been detected in 2004. Marshall et al. ATel 1668 report the analysis of the Swift/UVOT data of IGR J00291+5934. The source is detected in the UVW2 filter with a magnitude of 19.6. Compared to the other optical observations this suggest a very blue spectrum for the source More details in Chakrabarty et al. 2008 ATel 1660 Markwardt and Swank 2008 ATel 1664 Torres et al. 2008 ATel 1665 Russel et al. 2008 ATel 1666 Linares et al. 2008 ATel 1667 Marshall et al. 2008 ATel 1668 Stephen et al. ATel 1680 mention that an INTEGRAL source IGR J18246-1425 lies within the RXTE error box of the new intermitent X-ray pulsar XTE J1824-141. The 20-40 flux of IGR source is 1.1 mCrab. Markwardt ATel 1681 report the results of a Swift observation of this field and mention the presence of a source at RA= 276.09833, Dec=-14.415778 (error < 6 arcsec), therefore consistent with the IGR. No significant pulsations were present at the expected period of 120 seconds. The spectrum is highly absorbed, with Nh~ 8e22 cm2 (for a power law continuum, with Gamma=1.15). Markwardt reports the presence of 2MASS J18242381-1424509 a K=10 source within the XRT error circle as a plausible counterpart. He adds that the lack of pulsation of the Swift source prevents a firm association with the XTE source, however the variability of the flux may argue in favour of an association More details in Stephen et al. 2008 ATel 1680 Markwardt 2008 ATel 1681 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #283 July 22 2008 |
Goncalves et al. 2008, ATel 1623, report the results of their
spectroscopic observations of 2MASX J20183871+4041003,
the IR counterpart of IGR J20187+4041.
They report the detection of narrow emission lines of Halpha, N II, a doublet S II, and S III at z = 0.0144, plus stellar photospheric absorption in Ca II (3 lines) at the same redshift. They thus conclude that the near-IR continuum is dominated by starlight. All these are in good agreement with the I-band image shown in previous work. Based on these results Goncalves and colleagues tentatively classify the source as a Sey 2. The authors further discuss the properties of the Galaxy seen at other wavelengths (radio, X-rays) and add that the source is a low luminosity Sey, and refute the association of this object with EG J2020+4017 or AGL2021+4029. More details in Goncalves et al. 2008 ATel 1623 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #282 July 21 2008 |
Masetti et al. 2008, ATel 1620, report the results of
Optical spectroscopy on the counterparts of IGR J17404-3655
(USNO-A2.0 0525_28851523) and IGR J18173-2509.
IGR J17404-3655: The optical source shows a red continuum, with possibe absorption by Galactic dust on the line of sight with a single narrow emission line, consistent with Halpha (EW~17 Angstrom). The optical characteristics of the source lead the authors to conclude that this source is a Galactic X-ray source, and a likely LMXB. IGR J18173-2509: The optical source observed by the authors lies at RA = 18 17 22.25, Dec = -25 08 42.9 (from the DSS-II-Red survey astrometry). It shows a number of Balmer (up to Hdelta at least), HeI and HeII emission lines at z=0, superimposed on a rather blue continuum. By analogy with other sources the spectral characteristics of the source allows Masetti et al. to identify this object as a Galactic Cataclysmic Variable. More details in Masetti et al. 2008, ATel 1620 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #281 July 16 2008 |
Tomsick et al. 2008, accepted in ApJ
report the results of Chandra observations of the
field of 20 IGRs. The sources are IGRJ00234+6141, J01363+6610, J06074+2205, J09026-4812, J10101-5645, J11305-6256, J11435-6109, J14515-5542, J17200-3116, J17285-2922, J17331-2406, J17407-2808, J17445-2747, J17507-2856, J18193-2542, J18214-1318, J18256-1035, J18259-0706, J18325-0756, J18539+0727 In 12 cases do they find a counterpart within the INTEGRAL error box of which 11 have an Optical and/or IR counterpart. For each sources they provide the refine position, the spectral analysis with Chandra (value of Nh and power law photon index), the flux (and upper limits when no source is detected), and the magnitude(s) of the counterparts. From these analysis Tomsick et al confirm that IGRJ00234+6141 is a CV, that IGR J06074+2205, IGR J10101Ð5645, IGR J11305-6256, and IGR J17200-3116 are HMXBs, and that IGRJ14515-5542 is an AGN. They find that IGR J11435-6109 is an HMXB and IGRJ18259-0706 is anAGN. They also mention that IGR J09026-4812, IGRJ18214-1318, and IGRJ18325-0756 may be HMXBs. All details of the analysis, including the discussion on the type of sources even for those that do not have a Chandra counterparts can be found in Tomsick et al. 2008 arXiV 0807.2278 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #280 July 10 2008 |
Malizia et al. 2008, accepted in MNRAS
report the results of INTEGRAL and Swift
observations of 5 Sey 1s, 4 of which are IGRs:
IGR J14552-5133, J16175-5928, J16385-2057,
J19378-0617.
They first report that J16385-2057, J19378-0617 are Narrow Line Sey1 while J14552-5133 and J16175-5928 are candidates NL-Sey 1. They study the spectral characteristics of all sources, first from the INTEGRAL/IBIS data alone, then extending the analysis to a broader energy range with Swift/XRT. All sources from their sample have steeper spectra than the canonical value observed in Broad Line Sey1. This seems to be indicative of the presence of a cut-off or a break in the spectra, since both theses models provide a good fit to the 0.1-100 keV spectra. They add that in J16385-2057 a reflection hump is also necessary to represent the spectrum well. In order to improve the statistics, Malizia et al. combined all spectra from the 5 sources to build an average spectrum. The latter is well fit by an absorbed power law (Gamma= 1.82, Nh=2e21 cm-2) with a cut-off (Ec=38 keV) and a soft excess modeled with a black body with kT=70 eV. They report that a reflection component may be present, with a value compatible with those of BL-Sey 1. The authors further discuss their results and mention in particular that the differences seen with the BL-Sey 1 are compatible with NL-Sey 1 being younger objects accreting at higher accretion rates. More details in Malizia et al. 2008 arXiV 0806.4824 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #279 June 26 2008 |
Pandel et al. 2008,
ATel 1595 report the results of
XMM observations of the field of the variable
AGILE source in the Cygnus region.
They detect several sources including IGR J20187+4041 at RA=20h 18m 38.40s Dec=+40d 40' 58.4" (+-2.7" at 90%) The spectrum is well fitted by an absorbed power law with Nh=8e22 cm-2 and Gamma=1.2 for a 0.5-10 keV flux of 4.3e-12 erg/cm2/s. The flux and spectral parameters are consistent with those of a Swift observation performed in 2006, which indicate no variability between those two observations. More details in Pandel et al. 2008 ATel 1595 Trejo et al. 2008 Atel 1597 report E-VLBI observations of 2MASX J20183871+4041003 the counterpart to IGR J20187+4041 which was identified in radio with the VLA. Preliminary analysis of the data show a partially resolved source at RA =20h 18m 38.7347s Dec =40d 40' 59.984" (+-2e-3 arcsec) with a peak brightness of 0.72 +/- 0.05 mJy and an integrated flux density of 2.3 +/- 0.2 mJy. According to Trejo et al. the presence of a compact radio component makes 2MASX J20183871+4041003 an eligible candidate for being the counterpart to the variable gamma source in the Cygnus region. The authors add that the low density of the flux does not suggest recent flaring activity in the source. More details in Trejo et al. ATel 1597 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #278 June 26 2008 |
Blay et al., 2008, accepted in A&A,
report the results of observation of the SFXT IGR J17391-3021/XTE J1739-302.
with INTEGRAL and RXTE. The INTEGRAL data consist of GPS, GCDE and
data from the Galactic centre key project from AO 4 and 5.
They present the long term light curves of the source. They remark two different types of activity (outbursts): -the most numerous ones are the faintest, with a 20-40 keV rate of ~10 cts/s, that seem to last ~0.6h -the brightest are usually found at ~60 cts/s, and last for longer than ~1h The authors failed to find any coherent modulation up to 100 s. Blay and collaborators study the spectral characteristics of the source using ISGRI and JEM-X and add an RXTE/PCA spectrum. They mention, in addition to an absorbed exponentially cut-off power law continuum, the presence of broad absorption at 30 and 60 keV. But adding a Cyclotron Resonant scatering feature to the continuum does not improve the fit significantly. They further discuss their results within the framework of the clumpy wind models and conclude that these could explain well the properties of the source. They further allow them to predict an orbital period of ~8 days. Much more details can be found in Blay et al. 2008 arXiV 0806.4097 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #277 June 17 2008 |
Sazonov et al., 2008, accepted in A&A, report the results
of Chandra observations of 7 IGRs.
The sources in question are : IGR J02466-4222, J08390-4833, J09522-6231, J14493-5534, J14561-3738, J21343+4738, J23523+5844. They first refine the X-ray position to an accuracy of 2" (already appearing on the IGR pages). They then study the spectral and temporal behaviour of these sources and give a likely identification for all of them. IGR J08390-4833: The authors mention that the X-ray absorption measured with Chandra is less than the total Galactic absorption in this direction. They also report the discovery of a period of 1450s in the Chandra data. Optical and NIR counterparts are found in the USNO B1 and 2MASS catalogues with B = 17.65, R = 16.05, I = 16.83, J = 15.68, H = 15.29, and K = 14.52 The authors discuss the type of the object and favour a magnetic CV (IP) IGR J21343+4738: The R~14 USNO B2 object has a spectrum typical of a B3 star. Therefore the source is a HMXB All other sources are AGNs with significant intrinsic absorption. 2 of them, J02466-4222 and J14561-3738, are likely Compton thick AGN (Nh>1e24 cm-2). All details about individual sources can be found in Sazonov et al. 2008 arXiV 0802.0928 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #276 June 12 2008 |
Prat et al., 2008
accepted in MNRAS, report 34 simultaneous
RXTE and INTEGRAL observations of the High Mass X-ray
Binary IGR J19140+0951.
They present the orbital phase resolved spectral analysis of those data. In a first run they use a simple model of an absorbed power law, plus high energy cut off when required. They then fit the resulting 3-80 keV spectra with an absorbed comptonization model. The spectral parameters obtained further confirm that the system very likely hosts a neutron star orbiting a supergiant companion star. Prat et al. find an evolution of the photoelectric absorption strongly correlated with the orbit of the system. This behaviour is expected for a compact object deeply embedded in the wind of the companion. Using a wind model to explain this evolution, they find a wind mass-loss rate of ~5 E-8 solar masses/year, and an orbital inclination angle in the range 38-75 degrees. The other spectral parameters do not seem to be correlated with the orbital phase. The authors also detect a soft excess in 4 observations, at orbital phases consistent with the neutron star being behind the companion. This soft excess is interpreted as a reprocessing of the X-ray emission originating from the neutron star by the surrounding ionised gas. More details in Prat et al. 2008, arXiV 0806.1973 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #275 June 5 2008 | Butters et al., 2008 accepted in A&A, report RXTE observations of 3 high energy sources with the aim to identifying their nature. Of of the source is IGR J17195-4100. The authors perform timing analysis and find two equally possible periods in the periodogram of the source at 1842.4s and 2645.0s, both being significant at >4-sigma. These are typical of spin periods for Intermediate Polar. If the longer is the spin, and the other the beat period, then the orbital period is 1.7 hr. They also fit the spectra with 2 models consisting of an absorbed bremsstrahlung or an absorbed power law both with the inclusion of an iron line. The authors mention that the first model leads to a poor chi2 but they argue that this may be due to contamination by other sources in the PCA fov. Based on these results they suggest that the source is an IP although they cannot definitively classify it. More details in Butters et al. 2008 arXiV 0806.0751 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #274 June 3rd 2008 | Rodriguez et al., 2008 ATel 1554 report the results of observations of the field of IGR J19112+1358 with RXTE and Swift. The observations were made soon after the discovery of this source by INTEGRAL (24 April). The source is not detected by any of the two instruments in any of the pointings. Summing all Swift/XRT data together we estimate a 0.5-10 keV 3-sigma upper limit on the absorbed flux of the source of 6-17 E-14 erg/s/cm2 depending on the spectral slope adopted. More details in Rodriguez et al. 2008 ATel 1554 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #273 June 3rd 2008 |
Nespoli et al., 2008 accepted in A&A, report the results
of infra red spectroscopy of the IR counterpart of 6 HMXBs
5 of which also IGRs. For each source the authors report the spectra, presence of line, and provide an identification of the companion star, plus a estimate of the distance to the source. -IGR J16027-5129 is classified as a B1 Ia and therefore is a SgHMXB. The distance is estimated to 6.1 kpc, compatible (within the errors) with previous estimates. -IGR J16465-4507 is classified as a O9.5 Ia, and is therefore a SgHXB. The X-ray nature of the source leads to a SFXT nature as suggested in earlier works. The distance is estimated to 9.5 kpc, compatible (within the errors) with previous estimates. -IGR J16479-4514 is classified as a O9.5 Iab. The authors add that this together with the X-ray behaviour of the source lead them to classify the source as a SFXT. The distance is estimated to 2.8 kpc, compatible (within the errors) with previous estimates. -AX J1841.0-0536 (IGR J18410-0535) is classified as a B1 Ib and therefore a SgHMXB. Together with the X-ray properties this confirms the SFXT nature suggested earlier. The distance is estimated to 3.2 kpc. -IGR J19140+0951 is classified as B1 Iab, in agreement with the older suggestion of a B0.5 I, and therefore confirms the SgHMXB nature of the system. The distance is estimated to 1.1 kpc, compatible (within the errors) with previous estimates. In additon the authors add that for 4 systems (16465-4507, 16479-4514, 18410-0535, 19140+0951) the local absorption comes from material concentrated around the compact object. All SFXTs are strongly absorbed which, according to Nespoli et al. may be a signature intrinsic to the class. More details in Nespoli et al. 2008 arXiV 0806.0295 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #272 May 23 2008 |
Ibarra, Kuulkers, and Saxton, 2008 ATel 1527 report the first X-ray identification
of IGR J18307-1232, found through a cross-correlation of the
2st XMM-Newton slew survey catalog and the INTEGRAL survey
catalog.
XMMLS1 J183049.6-123218 is found inside the INTEGRAL error box. The XMM-Newton slew source coordinates are: RA = 18h30m49.6s, Dec= -12d32'18" (+-8" at 68% confidence), which is ~1.9' from the INTEGRAL position. The 0.2-12 keV flux is 2.6e-12 erg/s/cm2 (when assuming an absorbed power law with a photon index of 1.7 and Nh = 3e20 More details in Ibarra et al. ATel 1527 Landi et al. 2008 ATels 1538 and 1539 report the results of Swift follow ups of 6 sources (IGR J09253+6929, J10448-5945, J11098-6457, J13186-6257, J15529-5029 J17404-3655). They first give the refined position for each and identify ppossible counterparts at other wavelengths. They also provide spectral analysis of the XRT spectra. The web pages will be soon updated with the position and results while more details can be found in Landi et al. 2008 ATels 1538 , and 1539 Further to that Parisi et al. 2008 ATel 1540 report the results of Optical spectroscopy of two of the above sources (IGR J09253+6929 and IGR J11098-6457). IGR J09253+6929: Broad redshifted Halpha and Hbeta emissions, as well as narrow redshifted [OIII] emission lines, are detected. The authors determine a redshift z = 0.039 for this object, and conclude it is a Seyfert 1 AGN. IGR J11098-6457: The author discuss the type of the USNO-A2.0 source U0225_10613596 associated with the XRT source. The object shows a continuum typical of an M-type giant, with superimposed Halpha and Hbeta lines in emission and at redshift zero. While the presence of another XRT source slightly outside the INTEGRAL error (as discussed by Landi et al.) may suggest this source is not the INTEGRAL one, the author conclude that this XRT/USNO source is a symbiotic star. More details in Masetti et al. 2008 ATel 1540 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #271 May 23 2008 |
Sidoli et al. 2008 accepted in ApJ, report the results of the first four
months of a Swift monitoring of several SFXTs while outside
the outburst period. The sources in question are
IGR J16479-4514, J17391-3021 (XTE srce), J17544-2619, J18410-0535
(ASCA srce).
The authors detect in all cases a low level of X-ray activity , which they interpret as an evidence that these sources accrete matter even outside the outbursts. A large variability of the flux is also seen with many flares during those periods. The authors present lightcurve and spectral analysis of these monitoring. In the case of J18410-0535, they measure a spin period of 4.7008 s which indicates, compared to previous measurements, that there is evidence for spin up. The precise spectral parameters for each source are given: All sources display hard and highly absorbed (4e22 cm-2 < Nh <10e22 cm-2) spectra In J16479-4514 an outburst is also observed and the authors mention that there is no variation of Nh between the outburst and the long term value (see also below). The authors finally discuss these findings in the context of the different models proposed to explain the fast behaviour of these sources. In a paper by the same team, Romano et al. 2008 accepted in ApJ Letter focus on the rise to outburst of IGR J6479-4514 as seen with Swift. The authors present the 0.2-150 keV spectral analysis of 3 particular intervals during the rise of this source's outburst. The spectra are well represented with the standard models for pulsars X-ray binaries, ie cut-off power law or Comptonization. The authors mention that they do not find any evidence for variability of the absorption. They further discuss their results within the framework of models for SFXTs, and also suggest that the compact object in this source is probably a pulsar. More details in Sidoli et al. 2008 arXiV 0805.1808 and Romano et al. 2008 arXiV 0805.2089 Bozzo et al. 2008 accepted in ApJ, present theoretical consideration about the accretion in Supergiant High Mass X-ray binaries (i.e. wind accretion), and expand this to the particular case of SFXTs. The authors show that the only way to have large factor of luminosity variations is to have transition between the different regimes of accretion when direct accretion onto the neutron star is inhibited (eg sub and super sonic propeller, sub and super Keplerian regimes). Contrary to the usual interpretation of outbursts of SFXTs resulting from direct accretion of clumpy stellar wind, Bozzo et al. show that transition accross the magnetic and/or centrifugal barrier can explain the observed properties of those sources. This implies modest variations of the wind density and/or velocity. In this interpretation the SFXTs showing large variations and low spin for the pulsar must have magnetic fields of the same order as magnetars. The authors also test these hypothesis on IGR J17544-2619. They first conclude that the lowest level of emission is compatible with the emission from the supergiant companion. In two cases (magnetic barrier and low spin vs. centrifugal barrier and higher spin) the authors conclude that the magnetic fields inferred for the source are in the magnetar range. More details, including all equations, can be found in Bozzo et al. 2008 arXiV 0805.1849 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #270 May 6 2008 |
Monard, (VSNET alert 10167) report an improved period
for IGR J14536-5522. He found a value of
0.13153d +/- 0.0001d derived by considering sharp minima in the
(optical) lightcurves over a period of 29d.
More details on the vsnet pages at
http://www.kusastro.kyoto-u.ac.jp/vsnet/
Paltani et al. 2008 accepted in A&A, report a
hard X-ray survey of the Coma region.
SOme of the sources are IGRs. The authors study
the properties of all sources and esablish ratio
of Sey 1 vs Sey 2, present logN-logS, and discuss their
results.
More details in Paltani et al. 2008
arXiV 0805.0537
Sguera et al. 2008 accepted in A&A, present a long
term study of IGR J16479-4514, using
INTEGRAL and Swift.
They focus on 19 X-ray flares from this SFXT, 10 of
which are discovered in their study. All flares are well
fitted (in the ISGRI band) with either a power law
(Gamma=2.2-3) or a bremsstrahlung (kT=21-46 keV).
In one case a joint XRT/JEM-X/ISGRI spectrum is
studied.
The best model is an absorbed power law with
Nh=16e22cm-2 and Gamma=2.5, or equivalently
an absobed bremsstrahlung with Nh=9e22 and kT=19 keV.
The authors then accumulated data when the source is not significantly detected at the scw level (referred to as "quiescence"). They detect the source in the mosaic and present a spectral analysis of this quiescent state using first only ISGRI data. They, then, add the Swift/XRT spectrum and fit a broad band quiescent spectrum. An absorbed powerlaw or bremstrahlung fit the data equally well with Gamma=2.2 or kT=20 keV, with Nh=9e22 cm-2. Assuming a distance of 4.9 kpc they deduce an average 20-60 keV luminosity of 5e34 erg/s. The authors discuss their findings in the context of SFXT, and suggest that IGR J16479-4514 is a transition object between other SFXTs and classical SGXBs. More details in Sguera et al. 2008 arXiV 0805.0496 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #269 April 30 2008 |
Sidoli et al. 2008 ATel 1496 report on
Swift observations of the very faint X-ray transient
XMMUJ174716.1-281048/IGR J17464-2811
The XRT monitoring allows them to first report that IGR J17464-2811
is the first VFXT with a ``quasi persistent" behaviour.
Sidoli et al. indeed mention that on 28 Apr 2008, the source was still active, with a 0.2-10 keV unabsorbed flux of~3.3E-12 erg/cm2/s (with a power law model with Gamma=2.25, and Nh=9E22 cm-2). The source activity is therefore not decreasing, and they conclude that the duration of the last outburst is probably longer than 5 years. More details in Sidoli et al. 2008 ATel 1496 Ajello et al. 2008 ATel 1497 report on the presence of a source detected with Swift/BAT in the error box of the recently detected variable AGILE source in the Cygnus region. This source is positionally coincident with the INTEGRAL source IGR J20187+4041. The authors also re analyse 2 Swift/XRT observations. The XRT-BAT spectra are well fitted with an absorbed power-law with Nh=12.4e22 cm-2, and Gamma=1.6(+-0.2). The Jan. 2005-Mar. 2007 BAT lightcurve is consistent with being constant, and the XRT observations show moderate variability of a factor less than 2. The authors discuss their results, and in particular the possibility raised in ealier studies that this source is a blazar, and mention that other possibilities cannot be excluded. Further to that, Halpern 2008 ATel 1498 comments on the discussion about this source, and provides the results of optical observations. He first mentions that the galaxy 2MASX J20183871+4041003(the counterpart to the IGR source) is actually outside the EGRET error box, and that the claim that the 2MASX source has blazar-like characteristicsWas not based on any physical property of the galaxy (as e.g. the absence of a compact radio source). According to Halpern a relationship of the AGILE source to 2MASX J20183871+4041003 is problematic for similar reasons. He then report the results of an I-band image of 2MASX J20183871+4041003 from the MDM 2.4m telescope. A bulge and disk are clearly resolved, indicating that it is probably a nearby (z<0.1) Seyfert galaxy, which is in contrast with the fact that blazars are normally found in elliptical galaxies. Halpern rejects, in particularthe z=1.5+/-0.2 concluded earlier for this object. From a new Swift XRT observation of IGR J20187+4041, he further adds that there is no X-ray evidence of current blazar activity from this source. More details in Ajello et al. 2008 ATel 1497 and Halpern 2008 ATel 1498 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #268 April 28 2008 |
Kniazev et al. 2008 ATel 1488, report the
results of observations of IGR J08390-4833 with
the SAAO 1.9 m telescope.
They authors mention that a single optical object is found in the Chandra error box at a position RA=08h 38m 49.11s, Dec=-48d 31m 24.7s The 4000-7000A optical spectrum showed bright Balmer emission lines with zero redshift, which indicates that this is a Galactic object. According to the authors the spectrrum has an overall blue shape which, with the sequence of bright Balmer lines, is typical of accreting white dwarf binaries - cataclysmic variables. The source is therefore classified as a CV. More details in Kniazev et al. 2008 ATel 1488 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #267 April 25 2008 |
Carmona, Beckmann & Rodriguez 2008, ATel 1489,
report the discovery of a new source IGR J19112+1358
discovered with ISGRI during the last INTEGRAL
observation of GRS 1915+105.
The source lies at RA = 19 11 12.6 DEC= +13 58 52 (statistical error of 4'). The source is detected in 20-40 keV mosaic at 1.2+-0.2 cps (about 7 mCrab). IGR J19112+1358 is not detected in single scw, and in 40-80 keV mosaic either. It was not detected in our previous 1915+105 observation (on 2008-04-17) with a 3 sigma upper limit of about 4 mCrab. The IBIS/ISGRI spectrum can be represented by a single power law model with photon index 3.2+-0.8 and a model flux of 5e-11 erg/cm**2/sec (20-40 keV). We also add that within the ISGRI error box lies the infrared source IRAS 19089+1351 at 2.6 arcmin distance to IGR J19112+1358. More details in Carmona et al. 2008 ATel 1489 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #266 April 23 2008 |
Dean & Hill, 2008 accepted in A&A, discuss
the possible properties of the putative pulsar in
IGR J18135-1751/HESS J1813-178.
Assuming magnetic dipole losses, a conversion efficiency between dot(E) and L(20-100 keV) hard X-rays (1%) similar to other such sources, an age of 300 yrs, and distance of 4.5 kpc the authors find an extreme set of parameters for this type of object. P=0.55s dot(P)=3e-11 s/s and B=1.28e14 G. The authors explore several possibilities to reconcile the properties of the pulsar with more common parameters but these are either quite unlikely (d=45 kpc), or make it lie in an extreme anyway (conversion eff=0.01%). According to Dean & Hill, although some possibilities are not unlikely, the most likely explanation is that the pulsar was born with a spin not very different from its actual value. Hence the spin down age should be decoupled from the actual age, as has been seen in at least another such source. More details can be found in Dean & Hill, 2008 arXiV 0804.3420 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #265 April 14 2008 |
following the mention of a renewed activity of the SFXT
XTE J1739-302/IGR J17391-3021 detected with Swift
(ATel 1466), Chenevez et al. 2008 ATel 1471 report
that the outburst detected by Swift started in reality
5 hours earlier than the BAT trigger on April 4 2008, as
seen with INTEGRAL.
According to Chenevez et al., JEM-X onboard INTEGRAL detected a flare starting at 16:18 (UTC) on the same day during Galactic Bulge monitoring observations. The 3-10 keV (resp 10-25 keV) mean flux averaged over ~2 hours was 42 mCrab (resp. 80 mCrab). The 3-10 keV (10-25 keV) upper limits before the flare were 4 mCrab (resp. 8 mCrab). The authors also report tthe detection of the source by ISGRI with 20-40 keV (40-80 keV) fluxes of 31 mCrab (13 mCrab) over a 8 ksec observation. More details in Chenevez et al. 2008 Atel 1471 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #264 April 11 2008 |
Baldovin Saavedra et al.2008 ATel 1468
report that the transient IGR J17473-2721 seen recently
in activity continues to brighten in the IBIS and JEM-X
observations of the Galactic Bulge monitoring.
According to the authors the source flux has increased by a factor of 3 between 2008 April 08 and 2008 April 1. It is detected with ISGRI fup to ~250 keV with an average 20-250 keV flux of 2.7e-9 erg/cm**-2/s. The average persistent 3-10 keV (resp 10-25 keV) flux is 50 mCrab (90mCrab). Baldovin Saavedra et al. also report the observation of a 50s long burst UT 2008, April 08, 13:36, that reached an unabsorbed 0.1-100 keV flux of 3.7E-8 erg/cm**-2/s at the peak. A black body with temperature 2.4 keV was obtained for this burst. More details in Baldovin Saavedra et al. 2008 Atel 1468 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #263 April 9 2008 | Romano et al. 2008 ATel 1466 1466 report the detection of a new outburst detected by BAT onboard Swift on 2008-04-08 at 21:28:15. The 15-150 keV BAT lightcurve is nearly constant from T-119 to T+950 s. The authors performed a spectral analysis of two intervals (T0 to T+341s, and T+373s to T+850s). Both spectra can be fitted with simple power laws with photon indices consistent with being constant (2.7 and 3.0). The Swift/XRT light curve shows two distinct flares the 2nd half bright as the first. The photon indices are significantly harder than those obtained from the BAT spectra. This is the sixth episode of emission above 150 mcrab seen with the BAT. More details can be found in Romano et al. 2008 Atel 1466 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #262 April 4 2008 |
Altamirano et al. 2008 ATel 1459 report the results from a
Swift XRT observation of the source.
Their X-ray position is consistent with the Chandra position,
which therefore confirms the association of the IGR source
with the detection of a type I burst by Agile.
The XRT spectrum is well fitted by an absorbed power law
with Gamma=1.68 and Nh=3.8e22cm-2.
They also report the detection of a 100s long X-ray burst,
well represented by a black body of 2.3 keV, showing no
photospheric radius expansion.
From this they can deduce an upper limit to the distance
between 3.9 and 5.4 kpc.
In a following ATel (# 1461), Markwardt et al. 2008 add
that the RXTE monitoring scan of the source reveals persistent
activity from the source on 2008-03-28 and 2008-03-31 at 2-10
keV fluxes of about 13 and 18 mCrab. Previous scans were
consistent with quiescent level with 2 sigma upper limit of
6 mCrab.
Kuulkers et al. 2008, ATel 1461 report the detection of the source
with INTEGRAL/ISGRI during their Galactic bulge monitoring.
They report 18-40 keV and 40-80 keV fluxes of 41 mCrab
and 42 mCrab respectively, which, according to Kuulkers et al.,
indicates a hard spectral state.
During previous Galactic bulge monitoring observation on 2008 March 22
the source was possibly seen near the detection limit, with a flux of about
6.5 mCrab (18-40 keV).
Images and details can be found at
http://isdc.unige.ch/Science/BULGE/ (courtesy Erik Kuulkers) Kuulkers and collaborators further indicate that the source started to appear significantly in the daily averages of the Swift BAT observation on 2008 March 30, with a flux of 15-50 keV flux of 30mCrab. The source has been steadily increasing up to a daily average of ~45 mCrab. More details in ATel 1459, 1460, and 1461 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #261 April 1st 2008 |
Sidoli et al. 2008 ATel 1454 report the observation of
a new outburst from the SFXT IGR J17544-2619
seen with Swift.
Swift BAT triggered on March 31 at 20:50:45 UT. The light curve as seen with
BAT consists of a plateau from ~T-107 s to T+553 s with a ~8 s long peak at 546 s.
The spectrum during the plateau is well fitted with a simple power-law modelof
photon index 4.7+/-0.6. The 15-150 keV fluence is ~1.1E-06 erg/cm2, while
the 15-150 flux is 1.6544E-09 ergs cm-2 s-1.
The authors also report the results of Swift/XRT. They mention that from
T+170 to T+492s the light curve shows a complex morphology with
several flares.
After this, between T+3724 and T+5276s, the count rate has decreased by a factor of
~400.
During the peak of the outburst the XRT spectrum is hard, well fitted by a powerlaw
with a photon index of 0.74 absorbed by a column density NH=1.1E+22 cm-2.
Landi et al. mention that a cut-off power law provides a slightly better
representation of the spectrum, with a photon index -0.24, and a cutoff energy of 4.6 keV, with
a lower absorbing column.
They add that the source as significantly softened 1.5 hours after the main peak, with a spectrum consisting of an absorbed powerlaw of photon index 1.53 and Nh=1.1E+22 cm-2. More details in Sidoli et al. 2008 ATel 1454 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #260 March 31st 2008 |
Nespoli et al. 2008 ATel 1450 report
the results of Ks-band spectroscopy of
the counterparts of 2 IGRs, J16358-4726 and
J16393-4643.
According to the authors the two spectra are very similar,
with prominent CO absorption features between 2.29 and 2.40 µm,
a characteristic of late type stars.
They also report the presence of metallic lines.
The presence of He I 20581 A and Br-gamma might be indicate the
presence of a circumstellar disk around a compact object, although
the authors caution their genuineness.
The author add that their analysis rule out HXMBs since the companion are very likely late type stars most probably of K or M spectral type. They conclude that both companions are probably giants, and suggest that the systems are Simbiotic X-ray binaries. More details (including a list of notable lines) are given in Nespoli et al. 2008 ATel 1450 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #259 March 28th 2008 |
Sidoli et al. 2008 ATel 1444
report the results
of Swift observations of IGR J11215-5952 at
the quarter of its 329 d possible orbital period
(or half the 165 d one more recently suggested).
The source was not detected in either of the two observations. The 3sigma upper limits on the unabsorbed flux are 1.7E-12 and 2.3E-12 erg/cm2/s (1-10 keV) leading to a 1-10 keV limit of 1.1E-12 erg/cm2/s wile cumulating the two obs. At 6.2 kpc this is equivalent to a 1-10 keV luminosity of 5E+33 erg/s. More details in Sidoli et al. 2008 ATel 1444 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #258 March 27th 2008 |
Del Monte et al. 2008 ATel 1445
report the detection of a burst
with the super Agile detector onboard AGILE at a position
consistent with that of IGR J17473-2721.
The burst was detected on 26 March 2008, 23:19:40 UT, and
lasted ~40 s. It was significantly detected only in the
energy range 17-25 keV.
Assuming a distance of 8.5 kpc, the observed average flux corresponds to ~ 0.9e38 erg/s in the 17-25 keV range. The authors add that this flux is consistent with an Eddington limited flux for a neutron star mass. They propose that the burst is a Type I X-ray burst, which leads them to suggest that IGR J17473-2721 is an X-ray burster. More details in Del Monte et al. 2008 ATel 1445 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #257 March 21th 2008 |
Landi et al. 2008 ATel 1437, report
the results of a Swift/XRT observation
of IGR J18173-2509, recently associated with
XMMLS1 J181722.2-250838.
They refine the X-ray position to RA= 18h 17m 22.06s Dec= -25d 08m 40.47s (+-3.7" @90%). The authors add that within XRT error box two optical objects can be found on the DSS red plate. The X-ray spectrum is fitted by the combination of two power law of similar indices (Gamma~0.6), one being absorbed by the Galactic column density only, the other by higher absorption with Nh~6.7e22 cm-2. They further provide an XRT image at http://www.iasfbo.inaf.it/~landi/igrj18173-2509.html More details can be found in Landi et al. 2008 ATel 1437 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #256 March 20th 2008 |
Romano et al. 2008 ATel 1435, report that
the SFXT IGR J16479-4514 has entered a new outburst.
The outburst was seen with the BAT onboard Swift, and consisted of two flares, the second stronger than the first. The BAT spectra are respectively powerlaw-like and exponentially cut powerlaw-like for the first and second flare. The XRT also observed the source and the soft X-ray lightcurve is composed first of several flares, and in a second part it has declined to a lower flux. Romano et al. add that these peaks are more intense than any previous outburst. More details can be found in Romano et al. 2008 ATel 1435 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #255 March 11th 2008 |
Landi et al. 2008 ATel 1423
report the results of a Swift observation of
IGR J18325-0756. They first refine the X-ray position
to RA=18h 32m 28.30s Dec = -07o 56' 40.4" (+-4.1" ) Based on positional coincidence, the authors identify 2MASS J18322828-0756420 (J = 16.4, H = 15.3 and K = 14.5) as the probable IR counterpart. A flat power law spectrum with photon index ~0.8 (and Nh frozen to 1.5 e22 cm-2) fits the data well, although an index Gamma ~1.8 with Nh=1.5e23 cm-2 also provides a good description of the spectrum More details in Landi et al. 2008 ATel 1423 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #254 March 11th 2008 |
Panessa et al. 2008 accepted in A&A analyse
the broad band X-ray spectra of a sample of 9 Sey 1
objects with XMM and INTEGRAL.
5 of these objects are IGRs (IGR J07597-3842, J16482-3036,
J16558-5203, J17418-1212, J18027-1455).
They perform spectral analysis of the joint XMM and
INTEGRAL spectra and report the best spectral
models and results obtained in each case.
The basic model is composed of an absorbed power law
on top of which different additional features could be added:
J07597-3842: a soft black body and a narrow iron line are needed. A high energy cut-off represent the data better than a simple power law A reflection spectrum may represent the spectra better, but the reflection parameter is poorly constrained J16482-3036: a narrow gaussian is marginally detected at around 6.5 keV. The spectrum is best described by a cut off power law. J16558-5203: The best spectrum is a steep power law absorbed by a partially covering medium. Additional features may also be present, but their parameters are poorly constrained J17418-1212: a power law spectrum with reflection represents the data well. A narrow 6.3 keV line is present in the spectrum, while a second 6.74 keV line seems also present. J18027-1455: a cut off power law represents the spectra well. 6.4 keV and 6.67 keV lines are detected. The authors further discuss the spectral results, emission mechanisms and values of the parameters in the framework of AGNs. More details (including on the various spectral models tested in the course of their analysis) can be found in Panessa et al. 2008 arXiV 0803.0896 Kaur et al. 2008 accepted in MNRAS, report the results of Optical and X-ray observations of IGR J01583+6713. From analysis of optical spectrum of the counterpart the authors suggest the source is Be HMXB with the companion of spectral type B2 IVe. They also estimate a distance of 4 kpc. Their X-ray spectral analysis of 2 Swift and 1 RXTE observations shows that the absorption of the source is higly variable. The spectra can either be fitted by an absorbed powerlaw or an absorbed black body. Kaur et al. 2008 possibly detected a pulse with period 469.2s. Using the Corbet diagram and a max eccentricity for the system they estimate an orbital period of 216 to 561 days. More details in Kaur et al. 2008 arXiV 0803.1113 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #253 February 29th 2008 |
Ibarra, Kuulkers, & Saxton 2008 ATel 1397
report possible detection of IGR J18173-2509 and IGR J16426+6536
in XMM slew survey data.
For both sources the authors give the X-ray positions of the XMM source. These are: RA=18h17m22s Dec=-25d08'38" and RA=16h43m04s DEC=+65d32'53 (+-8" @ 1-sigma for both) For the former, the authors further add that XMMLS1 J181722.2-250838 and a Rosat source (1RXS J181723-250831) are the same based on the compatibility of the positions of the two X-ray sources , and their similar flux as seen with both XMM and Rosat. In the case of IGR J16426+6536, XMMLS1 J164303.7+653253 is found at the 4-sigma significance level only, but the authors estimate a low false detection probability for a random source (within a radius of 4.5') of ~0.5%. They further mention the presence of 2 additional Rosat sources in the INTEGRAL error box, and suggest that 1 of the three source may be the real counterpart. More details in Ibarra et al. 2008, ATel 1397 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #252 February 25th 2008 |
Nespoli, Fabregat and Mennickent, 2008 ATel 1396
report on the results of their K-band spectroscopy
of 2MASS J16492695-4349090 the proposed
counterpart of IGR J16493-4348.
No metal lines are detected. The authors report the detection of He I both in emission and absorption, and Brγ in absorption. From these results the author estimate the spectral type of this star to be B0.5 Ib. They further suggest the system is a neutron star (sg)HMXB. More details in Nespoli et al. 2008 ATel 1396 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #251 February 19th 2008 |
Rodriguez, Tomsick, & Chaty 2008 accepted in A&A
report the results of Swift observations of 12 IGRs.
The sources in question are IGR J02343+3229, J09523-6231, J10147-6354, J11187-5438, J13149+4422, J14579-4308, J16385-2057, J18490-0000, J18559+1535, J19308+0530, J19378-0617, J23524+5842. For all sources we give the refined X-ray position, which allowed us to identify possible counterparts at IR and optical wavelengths, and provide X-ray spectral analysis. When UVOT data are available we also give the UV magnitude of the counterpart. We confirm the nature of 6 sources formerly suspected to be AGN (IGRJ02343+3229, J13149+4422, J14579-4308, J16385-2057, J18559+1535, J19378-0617). We also suggest that IGR J09523-6231and IGR J10147-6354 are AGNs (the former has recently been confirmed as a Sey 1.5, and we suggest the latter is a Sey 2) All other sources may be X-ray binaries, although in just one case (IGRJ19308+0530) the Galactic nature is confirmed: the source has an F8 star as counterpart. We also report the discovery of six serendipitous (SWIFT) sources of unknown nature. More details in Rodriguez et al. 2008, arXiV 0712.1005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #250 February 19th 2008 |
Jonker, Torres & Steeghs 2008 accepted in ApJ,
report the results of I-Band optical and Chandra
observations of the accreting ms pulsar IGR J0291+5934.
The Chandra pointing allows the author to establish that the source was in true quiescence during the observation, with an unabsorbed 0.5-10 keV flux of 1e-13 erg/cm2/s Although the source is in quiescence in X-rays, the I-band lightcurve shows evidence for a strong flaring activity. After removal of the flares from the lightcurve, the author folded it on the orbital period, and report evidence for a sinusoidal modulation. They interpret this modulation as the result of superhump, and discuss the implication of such findings. The authors also compare their observations with previous quiescent observations of the same object in quiescence and discuss the possible origin and implications of the differences they observed. More details in Jonker et al. 2008, arXiV 0802.2394 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #249 February 14th 2008 |
Burenin et al. 2008 accepted in Astronomy letters,
report on their optical observations of several hard X-ray sources, 4 IGRs,
and one additional (IGR J16562-3301) they labeled so, although it was discovered
by SWIFT (note that it was given an IGR name in Krivonos et al. 2007). The 4
sources are IGR J01528-0326, J02343+3229, J03334+3718, and J13038+5348. For each source they give the position of the optical counterpart, and analyse medium and low resolution spectra. They confirm that the former two are Sey 2 associated with nearby nearly edge-on galaxies, while they report that the latter 2 are Sey 1. They also measure the redshift of those two sources. More details can be found in Burenin et al. 2008 arXiV 0802.1791 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #248 February 14th 2008 |
Chaty et al. 2008 have performed an intensive study of a sample of thirteen INTEGRAL
sources, through multi-wavelength optical to NIR photometric and spectroscopic observations.
By spectroscopic analysis of the most likely counterpart candidates they report the
spectral types of IGR J16320-4751, IGR J16358-4726, IGR J16479-4514,
IGR J17252-3616, IGR J18027-2016: they all host OB type supergiant companion stars, with IGR~J16358-4726 likely hosting a sgB[e]. They also confirm the supergiant O and B nature of IGR J17391-3021 and IGR J19140+0951 respectively, and the AGN nature of IGR J16558-5203.. While fitting the SEDs Chaty et al. find that IGR J16418-4532, IGR J16393-4643, are HXMBs, probably hosting a OB Sg and B III-IV star for the former and latter respectively, while IGR~J18483-0311 is likely a HMXB. They reject the proposed counterparts of IGR J17091-3624 and IGR J17597-2201, and propose two new candidate counterparts, that lead them to suggest that both sources are LMXBs (SED fitting). Chaty et al. also report that the NIR fields of four sources of the sample exhibit large-scale regions of absorption. While showing that the majority of those sources are HMXBs, Chaty and collaborators confirm that INTEGRAL is revealing a dominant class of obscured and short-living high-energy binary systems. They finally suggest an association of these systems with regions of the Galaxy exhibiting large-scale absorptions. More details in Chaty et al. 2008, accepted in A&A, arXiV 0802.1774 Rahoui et al. 2008 report on mid-infrared (MIR) observations of the companion stars of twelve supergiant X-ray binaries, some being obscured sources, and others being SFXTs. The main goal of this study is to disentangle the contribution of the star from that of the material enshrounding the system to the total emission. Rahoui et al. obtained the broad-band SEDs of the counterparts and fitted them with a combination of two black-bodies representing the emission from the star and that of MIR excess due to the absorbing material enshrouding the star, when needed. A MIR excess is detected in the emission of IGR J16318-4848, IGR J16358-4726 and possibly IGR J16195-4945. The other sources do not exhibit any MIR excess even when the intrinsic absorption is very high. The authors argue that in IGR J16318-4848 and probably IGR J16358-4726, the MIR excess is probably linked to their sgB[e] nature and therefore the presence of an equatorial disk around the supergiant companion in which dust can be produced. They also mention that supergiant stars in SFXTs could less absorbed than supergiant stars in obscured SGXBs, due to the geometry of the systems. They finally confirm the binarity of the absorption component, confirming the presence of a very dense cocoon of material around the compact object, as the extinction in the X-ray domain is generally several order of magnitudes higher than the extinction in the visible. More details in Rahoui et al. 2008 accepted in A&A arXiV 0802.1770 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #247 February 11th 2008 |
In a recently submitted paper (therefore all results will be sent
when the paper is accepted) Sazonov et al. 2008 report Chandra observations
of 7 INTEGRAL sources which allowed them to refine the X-ray positions to
about 2-2.5" accuracy (due to large offset pointings in order to avoid photon
pile up).
These sources are: IGRJ02466-4222, IGRJ08390-4833, IGRJ09522-6231, IGRJ14561-3738, IGRJ14493-5534, IGRJ21343+4738, and IGRJ23523+5844 The IGR main page is updated with these new positions. Masetti et al. 2008 accepted in A&A report optical spectroscopy of the tentative counterparts of 39 hard X-ray sources (35 IGRs). I just indicate here which sources are the targets, and each source's entry in the site is now updated. The targets are IGR J00040+7020, IGR J00256+6821, IGR J01528-0326, IGR J02343+3229, IGR J02504+5443, IGR J03334+3718, IGR J06117-6625, IGR J06292+4858, IGR J07437-5147, IGR J08023-6954, IGR J09446-2636, IGR J09523-6231, IGR J11366-6002, IGR J12131+0700, IGR J13038+5348, IGR J13109-5552, IGR J13149+4422, IGR J14298-6715, IGR J14331-6112, IGR J14471-6414, IGR J14561-3738, IGR J14579-4308 (IC 4518a), IGR J15161-3827, IGR J15539-6142, IGR J16024-6107, IGR J16056-6110, IGR J16385-2057, IGR J16500-3307, IGR J18027-2016 (SAX J1802.7-2017), IGR J18048-1455, IGR J18483-0311, IGR J19405-3016, IGR J21272+4241, IGR J23308+7120, and IGR J23542+5842 An important result is that among the sample of observed sources 29 are AGNs (13 Sey 1, 15 Sey 2 and a possible BL Lac), 5 are HMXBs, 2 are LMXBs, 1 is a CV (IP), one is a symbiotic star, and 1 is an active star. All details and precise results can be found in Masetti et al. 2008 accepted for publication in A&A arxiv 0802.0988 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #246 February 4th 2008 |
Parisi et al. 2008, ATel 1375, report on optical spectroscopy of
the field of IGR J00333+6122.
Focussing on USNO-A2.0 1500_00589511 which is consistent with the source labelled 1 in Landi et al. ATel 1322, the authors report the presence of several emission features in the optical spectrum. Of particular importance they point a very broad Halpha+[NII] complex and narrow [OIII] lines. Using the latter, they determine a redshift z=0.105+-0.001 for the source. They, in addition, mention that the source labelled 2 in e.g. Landi et al. is with TYC 4015-206-1 a star of intermediate spectral type that does not show any peculiar spectral features. They further argue that this point associated to the soft X-ray spectrum of this source, show that it is not a symbiotic X-ray binary, but a star with coronal emission, which rules out its association with IGR J00333+6122. They conclude that IGR J00333+6122 is the X-ray counterpart to USNO-A2.0 1500_00589511, and therefore a Seyfert 1 AGN More details in Parisi et al. 2008 ATel 1375 |
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| Mail #245 February 1st 2008 |
De Rosa et al. 2008 accepted in A&A, report high energy
observations with several satelittes (Chandra, XMM, ASCA, INTEGRAL)
of a sample of Sey 2 AGN detected by INTEGRAL, some of them discovered
with the latter (IGR J07565-4139, J12026-5349, J14579-4308(IC4518A),
10404-4625).
For all sources the authors report the results of their spectral analysis, give the value of Nh, and show that all those sources are absorbed although they are Compton thin. For all sources the broad band spectra are well fitted by an power law with an exponential cut-off which seems to indicate that the cut-off is a common feature in those sources They also report the presence of a Compton reflection component in J12026-5349, J14579-4308, and J10404-4625. At soft energy a soft excess is found in all sources but J07565-4139. The authors further discuss their findings in the context of AGNs, emission processes. They in particular discuss the origin of the reflection component and that of the iron line sometimes detected. Much more details can be found in De Rosa et al., 2008, astro-ph 0801.4675 |
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| Mail #244 January 21 2008 |
Bikmaev et al. 2008
ATel 1363
report the results of optical observations of 2 IGRs reported in the
hard X-ray INTEGRAL catalogue of Krivonos et al. 2007
IGR J23206+6431: The source was observed by SWIFT/XRT and is associated with 2MASX J23203662+6430452, preliminary classified as a galaxy by 2MASS catalog. The authors report th presence of an extended object at the position of the 2MASX source (Rc ~ 19 mag) from their analysis. The optical spectrum is heavily reddened due to the high Galactic absorption in this direction. It also shows redshifted and broad H-alpha and narrow [ O III ] emission lines. They measure a redshift of z=0.07173. The estimated de-reddened optical luminosity of the source is ~ 1e44 erg/sec. These results lead them to classify the source as a Sey 1. The best optical position from their data is R.A.(2000.0) = 23 20 36.576, Dec. = +64 30 45.15 IGR J02524-0829: This source is associated with the nearby edge-on spiral galaxy MCG-02-08-014. The optical spectrum of the nucleus of this galaxy shows redshifted narrow H_alpha; [NII] and [ S II ] lines in emission. The line ratio lead the authors to conclude that this source most probably a Sey 2, which seems confirmed by the spectrum from 6dFGS DDR2. A redshift of z=0.016721 was, then, obtained. More details in Bikmaev et al. 2008, ATel 1363 |
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| Mail #243 January 15 2008 | Bouchet et al. 2008 report a catalogue of point sources detected by SPI. Among them, a certain number of IGRs are seen with the Spectrometer. More details in Bouchet et al. 2008 accepted in ApJ, astro ph 0801.2086 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #242 Jan 3 2008 |
Landi et al. 2007, ATels 1322 and 1323 gives refined
X-ray positions, basic spectral parameters of 7
sources (IGR J00333+6122, J17487-3124, J18485-0047, J21272+4241,
J05270-6631, J17448-3232, J19267+1325) observed
with Swift. They also report, when found,
counterparts at other wavelengths. All details in Landi et al. 2007 ATel 1322 and ATel 1323 Further to that Jonker & Kuiper 2007 ATel 1326 report a Chandra HRC-I observation of IGR J00335+6126 (=IGR J00333+6122). Confirming the results from Landi et al. the authors found 2 sources in the INTEGRAL error circle. The positions are RA= 00h 33m 18.41s DEC= 61deg 27' 43.1" and RA= 00h 33m 57.71s DEC=61deg 26' 33.4" ( +-0.6" @ 90%) for the 1st and 2nd source respectively. The authors conclude that source 1 is a symbiotic X-ray binary, and that, thanks to their improved position the point source 2MASSJ00331833+6127432 (J=15.665, H=14.379, K=13.081) is the probable IR counterpart. More details in Jonker & Kuiper 2007 ATel 1326 In a letter accepted by A&A Leyder et al. 2008(astro ph 0712.1491) report the discovery of a new source in the field of Eta Car, with IBIS/ISGRI. IGR J10447-6027 is found at a significance of 5.8 sigma in the 22-100 keV range. It lies at RA= 10h 44m 47s Dec=-60deg 27' 15" +-3.4' at 90% Based on the spatial coincidence with a massive youg stellar object (URAS 10423-6011) the authors suggest that the source could be a new HMXB or signature of accretion and/or article acceleration in the YSO. More details in Leyder et al. 2008 astro-ph 0712.1491 Hill et al. 2008 (accepted in MNRAS astro ph 0712.2134) report X-ray analysis of IGR J16493-4348 mainly with Swift and INTEGRAL. They first report a refined INTEGRAL position which rules out the formerly proposed association of the source with PSR J1649-4349. The Swift position is in agreement with the INTEGRAL one and is: RA=16h 49m 26.6s DEC=-43deg 49' 10.5" +-3.6" at 90% confidence. They then identify a 2MASS (2MASS J16492695-4349090) and a Spitzer (SSTGLMC G341.3752+00.5829) source as probable counterpart. The SED of the counterpart may either suggest it is a main sequence dwarf star at 200-300 pc or a cool red giant at 2-3 kpc, or even an early type with kT>11 000 K at 7.5-22 kpc. The analysis of the X-ray data (spectral and temporal), in conjonction with the informations obtained from earlier Chandra and RXTE observations, lead Hill et al. to conclude that the source is an X-ray binary probably a high mass system, although a low mass companion cannot be completely excluded. More details in Hill et al. 2008 astro-ph 0712.2134 |
2007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #241 Decembre 7 2007 |
Although the paper is not accepted I point out
that we (Rodriguez, Tomsick and Chaty, 2007 submitted
to A&A) report refined X-ray positions for 12 IGRs
that have been observed with Swift.
More details will be given when the paper is accepted, but the refined positions will be provided on the web pages. |
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| Mail #240 Decembre 5 2007 | Grebenev et al. 2007,
ATel 1319, report the detection of
a new X-ray source with INTEGRAL/ISGRI during observations
of the Sgr Arm tangent region.
This source was detected on Oct. 12 2007, over the 7 hours of
exposition at R.A.=18h46m16s, Decl.=-02d23m12s (+-2 arcmin). The 18-45 keV flux was ~17mCrab on the average, with a peak of 35mCrab. The source was detected up to 70 keV and its spectrum could be described by a power law with Gamma=-2.7. It was not detected during 2 consequent observations with 3-sigma upper limits of 8.7 and 6.5 mCrab, which indicated that the source switched off. The authors discuss those properties and suggest that it could be another fast X-ray transient with a high mass and possibly a supergiant companion. More details in Grebenev et al. 2007 ATel 1319 |
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| Mail #239 November 30 2007 | Sguera et al. 2007, ATel 1313, mention that in the error box of the Cygnus Region source recently detected by AGILE ie a certain number of high energy (E>10 keV) sources. Amongst all of them they suggest IGR J20188+3647 -a very variable and detected by IBIS in only one observation- as the possible counterpart to the AGILE source. More details in Sguera et al. 2007 ATel 1313 while some images can be found here | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #238 November 29 2007 | Landi et al. 2007,
ATel 1310 report the results of a
Swift observation of the field of NGC 4180.
Their results lead them to suggest to rename the
source detected by INTEGRAL (formerly thought to be
NGC 4180) IGR J12131+0700 for the following reasons:
Two sources are detected by Swift/XRT within the IBIS error box of 5.1': Src 1 lies at RA = 12h 12m 49.62s, Dec = +06d 59s 44.6s (+-5.1 arcsec) Src 2 lies at RA= 12h 12m 56.60s, Dec= +07d 03s 06.7s (+-6 arcsec) The first object is coincidident with SDSS J121249.84+065945.4 (=NVSS J121249+065950) a QSO at z = 0.2095 It has a 2-10 keV flux of 1.5 e-13 erg cm-2 s-1 The other has no obvious association in Simbad, NED or HEASARC and is characterized by a 2-10 keV flux of 0.8 e-13 erg cm-2 s-1 The authors mention that no excess emission is detected at the position of NGC 4180, but the latter may still be the counterpart of the IBIS source, if it is heavily absorbed, i.e. it is a Compton thick AGN. However, due to the complexity of this field, the author suggest to rename the IBIS source IGR J12131+0700. See Landi et al. 2007 ATel 1310 |
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| Mail #237 November 21 2007 | Landi et al. 2007,
ATel 1288 report some more results from Swift/XRT
observations of IGR sources that are candidate
AGN. These are IGR J11366-6002, J16024-6107, J19405-3016, J22292+6647, and J23308+7120. For each the refined X-ray position allowed them to find counterparts at other wavelengths, in particular in Infrared and radio, that are classified as galaxies. They also report a preliminar spectral analysis from the XRT data. >/P> More details on the individual sources can be found in Landi et al. 2007 ATel 1288 Cheung et al. 2007 ATel 1289 report inspection of radio images from the field of IGR J18175-1530. The authors discuss the difference between the images of MAGPIS and NVSS, and indicate first that the radio source has varied between the epoch of the two observations. They also mention that the source is persistent over many years. They tentatively give a slop for the radio spectrum of -1.6 and -0.9 which indicate a non thermal emission. However the uncertainties in the spectral slopes due to variability and resolution preclude any definitive interpretation for the type of the source. More details in Cheung et al. 2007 ATel 1289 |
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| Mail #236 November 14 2007 | Landi et al. 2007,
report Swift XRT observations of several INTEGRAL sources
from the 3rd IBIS catalogue.
For all of them they give the refined position, and results
of preliminary spectral analysis.
For 6 of them, the swift XRT position confirms the previously
reported association with AGN.
The 6 AGNs are : IGR J00040+7020, IGR J00256+6821, IGR J01528-0326, IGR J02504+5443, IGR J16056-6110, IGR J16119-6036. The 6 other sources are: IGR J14298-6715, IGR J14331-6112, IGR J14471-6414, IGR J17445-2747, IGR J18249-3243, IGR J18256-1035 All positions will be put on the IGR web page, and more details can be found in Landi et al. 2007 Atel 1273 and Atel 1274 |
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| Mail #235 November 12 2007 | Kuulkers et al. 2007, ATel 1266 report that the source was also active 1.5 month earlier as seen from their Galctic Bulge monitoring programme. The authors also mention previous periods of activity which rule out the 165 days recurrence period suggested for this source More details in Kuulker et al. 2007 Atel 1266 Futher to this Walter & Zurita point out that in a recently accepted paper (http://arxiv.org/abs/0710.2542) they reported the occurrence of 8 flares seen with INTEGRAL/ISGRI. They mention that about 1 flare occur every 10 days of observation on average. More details about the structure of the wind and its clumpiness can be found in their paper. More details in Walter & Zurita Atel 1269 and astro-ph 0710.2542 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #234 November 9 2007 | Krimm et al. 2007, Atel 1265 report the occurrence of an outburst from the SFXT IGR J17544-2619 detected with the BAT onboard Swift. The source was first detected at a 15-50 keV flux of 190 mcrab at 1:31:04 UT on Nov. 8, 2007. It was above 100 mcrab over the next several hours and was seen at ~165 mcrab at 6:07:11 UT. According to Krimm et al. the source is usually below the detection threshold of the BAT and it was not detected 1.5 hours before the start of the outburst . More details in Krimm et al. 2007 Atel 1265 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #233 October 31 2007 | Revnivtsev et al. 2007,
ATel 1253,
report the identification of IGR J06239-6052.
Through observations with Swift the authiors first refine the position of the source to RA=06h 23m 45.613s Dec=-60deg 58' 45.39" (+- ~4 arcsec) This refined position clearly indicates that the IGR source is an active nucleus in the galaxy ESO 121-IG 028. This Galaxy is at z=0.040521. A preliminary spectral analysis shows the source is highly absorbed with NH~2e23 cm-2, which indicates the source is a Seyfert 2 galaxy. More details in Revnivtsev et al. 2007 Atel 1253 |
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| Mail #232 October 26 2007 |
Markwardt et al. 2007 ATel 1249 mention
that the newly discovered source IGR J18175-1530
was detected by RXTE in September and designated
XTE J1817-155.
The best fitting position obtained with RXTE is fully consistent with that of INTEGRAL. The 2-10 keV fluxes derived from the PCA scans had a peak of ~6 mCrab between 1 to 11 Sep 2007. Markwardt et al. mention no detection after 24 Sep with typical 2 sigma upper limits of about 1.5 mCrab (2-10 keV) More details in Markwardt et al. 2007 Atel 1249 |
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| Mail #230 October 25 2007 |
Paizis et al. 2007 ATel 1248 report the detection of
a new transient IGR J18175-1530, discovered with ISGRI
onboard INTEGRAL. The source position is RA= 18h 17m 34.3s, DEC= -15deg 30' 41" (+-2.5' statistical error) The source is detected at about 9 mCrab in a combined ~307 ksec observation. IGR J18175-1530 is also detected also in the single revolution sky maps but not at the science window level Paizis et al. mention that it was not detected in an XMM-Newton observation of the source position performed on 2003-04-10. They derive upper limits of 4e-13 ergs/cm/cm/s and 7e-13 ergs/cm/cm/s for the observed and unabsorbed source flux, respectively. The authors also note that the radio source GPSR5 15.308+0.226 (RA = 274.41058, DEC = -15.52519, Becker et al. 1994) is 1.3' away from IGR J18175-1530, well within the IBIS/ISGRI location error (2.5'). More details in Paizis et al. 2007 Atel 1248 |
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| Mail #230 October 19 2007 |
Moon et al. 2007 (accepted in ApJL)
report the results of Spitzer observations of two
absorbed sources one of which being IGR J16318-4848.
They report the identification in the mid infrared spectra of two continuum component a hot (1040 K) and a warm (190 K) one. They attribute these emission to two circumstellar dust components, one warm and one hot. They also report the detection in the spectra of many emission lines. While the majority are HI lines, the also observe the presence of metallic forbidden lines (Ne II, Ne III, S III, Si II, Ni II, Fe II), pure rotational H2 lines, and PAH emission . From these lines they deduce the presence of ionized stellar wind, an extended low density ionized region, and a photo dissociation region. They discuss the properties of the lines in question and deduce that the X-ray source is not the primarily responsible for the emission of forbidden lines although it can have some contribution. They also discuss the origin of the dust components, and indicate that both dust components contibute very little to the total Optical extinction. Finally they suggest the highly obscured X-ray binaries could represent an unknown evolutionary phase of XRBs with early type Optical companions. More details can be found in Moon et al. 2007 accepted for publication in ApJL astro-ph 0710.3351 |
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| Mail #229 October 15 2007 |
Negueruela et al. 2007 ATel 1239
in a deeper search for an optical counterpart to IGR J11435-6109
confirm the identification of 2MASS J11440030-6107364
= USNO-B1.0 0288-0337502 as the correct counterpart.
The authors give results from spectroscopic SAAO 1.9-m telescope observations of this source. Below 5000A the source is too faint to be detected. The 5000-7800A spectrum shows a strong H-alpha emission line on top of a reddened continuum. The authors interpret the -26A EW and lack of any other obvious stellar features as evidence for the source being an obscured Be star, compatible with the position of IGR J11435-6109 in the Corbet diagram. Negueruela and collaborators also discuss the results of some photometric observations made with the NTT. They obtain magnitudes: B=17.71, V=16.43, R=15.44. Based on the colors and color excess the authors discuss the distance of the source and mention that even for a B2Ve counterpart the source is at least at 6 kpc. More details in Negueruela et al. 2007 ATel 1239 |
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| Mail #228 October 9 2007 |
Tomsick et al. 2007 , ATel 1231 report the results of their
Chandra observation of the field of GR J11435-6109
They refine the X-ray position to R.A. = 11h 44m 00s.31 Decl. = -61d 07' 36".5 (+- 0".6 @ 90%). The energy spectrum is consistent with an absorbed power-law with an photon index ~1.0, Nh~10 e22 cm-2, and a 0.3-10 keV flux of 4.8e-12 ergs/cm2/s. Several arguments make it nearly certain that this Chandra source is the correct counterpart for IGR J11435-6109. Thanks to the refined X-ray position, Tomsick et al. identify USNO-B1.0 0288-0337502 as the very probable counterpart. It has magnitudes of B = 16.6, R = 15.7, and I = 14.8. This source also appears other Optical/infrared catalogs with J = 13.00 , H = 12.34, and K = 11.852, I = 14.5, J = 13.02, and K = 11.81. These suggest the counterpart is an HMXB. The author further mention that the brightness in optical indicates that significant amount of the absorption is intrinsic to the source. Finally they dismiss the previously proposed counterpart USNO-B1.0 0288-0337948 for which no X-ray emission is found in the chandra observation. More details in Tomsick et al. 2007 ATel 1231 Sidoli et al. 2007, accepted in A&A report Swift, XMM and INTEGRAL observations of IGR J11215-5952, the Supergiant Fast X-ray Transient. Their Swift observations revealed a secondary outburst as bright as the one observed 165 days earlier. They also report the detection of a pulse period at 186.9 s compatible with that found with RXTE. The XMM observations showed the outburst could be divided in two intervals: a bright and a faint one, both well fitted with absorbed cut-off power-laws. The authors then discuss the possible origin of the X-ray emission in IGR J11215-5952, and based on the narrowness of the peak exclude a purely spherical and symmetric wind accretion. Instead the authors discuss several geometries, that may explain short outbursts in HMXBs, and suggest that either the neutron star crosses a dense equatorial wind of the secondary once per orbit, and then the true period is 165 days, or the orbit is circular and the NS crosses the equatorial wind of the secondary twice per orbit, and the period is ~330 days. They also propose alternative geometries for other SFXT and HMXBs More details can be found in Sidoli et al. 2007 accepted in A&A astro-ph 0710.1175 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #227 September, 20 2007 |
Bassani et al. 2007 ,
accepted in ApJL, report their results on the identification of
IGR J22517+221.
The associate this IBIS source (first reported
in Krivonos et al. 2007) with MG3 J225155+2217
a z=3.668 quasar.
They analyse soft (Swift/XRT) and hard (INTEGRAL/ISGRI)
spectra of the source, and report : - a hard power law with Gamma around 1.5 - a curvature at soft X-ray, either due to intrinsic absorption, or indicative of the presence of a broken power law - flux variability over a period of 6 days. Looking in the archives, Bassani et al. construct a SED of the object and further discuss its properties. IGR J22517+2217 is radio loud and a broad line emitting quasar which also hosts a narrow line absorbing system. Most of these properties suggest the source is a blazar In addition the SED, when compared to other such system, is quite atypical, with either the synchrotron peak in the X/gamma ray band, or the Compton peak in the MeV range. More details can be found in Bassani et al. 2007, astro-ph 0709.3023 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #226 September, 14 2007 |
Molina et al. 2007 ,
accepted in MNRAS report broad band
analysis of the broad line radio galaxy IGR J21247+5058.
From the analysis of radio data, the authors mention
that the morphology of the (radio) source is typical
of that of an edge-brightened FRII.
They estimate the viewing angle to theta=35deg, which
seems small enough to peer into the broad line region
and may explain thre broadening of the Halpha line.
Using XMM-Newton observations they refine
the X-ray position of the core to RA=21h 24m 39.36s Dec=+50deg 58' 23.86" which is consistent with the position of the radio core. Their X-ray spectral analysis (using XMM-Newton, INTEGRAL, and Swift)suggests complex absorption due to two layers of material that cover partially the source with different covering fractions. The high energy nd of the spectrum shows the presence of a cut-off at ~75 keV. Molina et al. also report a possible evolution in the source absorption related to flux variations. Finally the authors conclude that the only to reconcile IGR J21247+5058 with being a Sey1 is if the torus surrounding the source is not continuuous but clumpy, ie composed of clouds with Nh~1e22-1e23 cm-2. More details can be found in Molina et al. 2007, astro-ph 0709.1895 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #225 September, 4 2007 |
Helfand et al. 2007 ApJ, 665, 1297
report the results of a Chandra observation of HESS J1813-178/
IGR J18135-175. The authors resolved the X-ray emission into emission from a point source surrounded by structure diffuse emission, whose morphology, according to them, ressembles that of a pulsar wind nebula. The refined position for the inner point source (the pulsar) is RA= 18h 13m 35.166s Dec= -17¡ 49' 57.48" +- 0.3 " at 1 sigma (this source is thereafter labeled CXOU J181335.1-174957) They then perform a spectral analysis of 3 different regions, namely the pulsar, an inner nebula and the PWN itself. Both the PWN and the pulsar spectra are well fitted with a power law of similar index Gamma=1.3. They find an absorption column density of 9.8e22 cm-2 and report a 3-sigma upper limit of 27% on the presence of a pulse for period greater than 6.5 s. The authors discuss their findings and conclude that the remnant asociated to the high energy source (G12.82-0.02) is associated to a young rotation powered pulsar. They also give a tentative distance to the source of 4.5 kpc which is adopted in their calculations. They can estimate a dE/dt=4 e 36 erg/s. They further discuss the possible origin of the TeV energy, and after remarking that this object is the one having the highest LTeV/Lx ratio they also mention that all PWN HESS source are found where high energy particle accelerator are close to HII regions. More details can be found in Helfand et al. 2007, ApJ, 665, 1297 Del Santo et al. 2007 ATel 1207 report refine distance estimates for XMMU J174716.1-281048/IGR J17464-281. Based on INTEGRAL analysis of the radius expansion of X-ray burst from the source they derive a distance of about 8 kpc, supporting the source being within the Galactic Centre region. More details can be found in Del Santo et al. 2007 ATel 1207 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #224 September, 4 2007 |
Torres et al. 2007
report Optical, near infrared and X-ray observations of the
accreting ms pulsar IGR J00291+5934.
They first monitored the decay of the 2004 outburst and then
observed the source when in true quiescence.
They refined the position of the Optical counterpart to RA=00h 29m 03.5s +- 0.01s Dec=+59° 34' 18.93" +-0.05" (the error being the rms of the 4 measurements from which the position was estimated) From their monitoring they could determine a rate of decline of 5.2 day/mag in the R band, and then estimate a peak brightness of R=17.03 mag The magnitude of the counterpart in quiscence is determined to R=23.1 The authors also report the presence of emission lines in the spectra of the counterpart and discuss their origin, and the physical implications for the system. While establishing SED they report the presence of a near infrared excess that may be due to a jet. In quiescence the source X-ray (0.5-10 keV) flux is 7.9e-14 erg/cm2/s but variability is reported. The authors further discuss their results, and give in particular estimates for several parameters of the system: The inclination angle is constrained to be between 22 and 32 degrees, The mass of the donor between 0.04 and 0.11 solar masses (for a 1.4 Msol neutron star) The distance to the source is also constrained to be between 2 and 3.4 kpc and the NS B field is less than 3e8 G. In addition several f their findings are discussed in the context of accretion in Soft X-ray Transients, and accretion onto magnetic compact objects. More details can be found in Torres et al. accepted by ApJ, astro-ph 0701095 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #223 august 9 2007 |
Sidoli et al. 2007 ATel 1174 report the results of the
last two Swift XRT observations of an ongoing monitoring
on XMMUJ174716.1-281048/IGR J17464-2811.
The source is detected with an unabsorbed 2-10 keV fluxes of 5.3E-12 erg/cm2/s and 2.2E-12 erg/cm2/s for the first and second observations respectively, assuming a power law model with Gamma=2.25 and Nh= 9E22 cm-2. The authors further mention that when comparing these values with the previous measurements since 2003 a complex light curve is revealed. This light curve is not compatible with a simply linear decay More details in Sidoli et al. 2007 ATel 1174 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #222 July 24 2007 |
Romano et al. 2007 ATel 1151,
report the detection of an outburst from the Supergiant Fast X-ray Transient
IGR J11215-5952 detected with Swift XRT. These authors are performing a campaign to study the source in quiescence an near apastron. They report that IGR J11215-5952 was not detected in their first 7 observations (from June 5 and July 17) with 3-sig upper limits of 3e-13 erg/cm2/s, but it was clearly detected on July 24. The 1-10 keV unabsorbed flux reached 1.4e-10 erg/cm2/s, for a spectrum that is well represented by a power law with Gamma=0.87 absorbed with Nh=1.08 E22 cm-2 This occurs 165 days after the preceding outburst at half the period reported previously. More details in Romano et al. 2007 ATel 1151 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #221 July 23 2007 |
D'Avanzo et al. report the results of their
Optical and Infra red observations of the field
around IGR J00291+5934 during quiescence.
They clearly detect the source in VRIJ and H bands while provide an upper limit in K. The best position they obtain is RA = 00h 29m 03.07s DEC= +59d 34' 19.12" with an uncertainty of 0.4". The reported magnitudes are : V=24.0, R=23.2, I=22.4, J=21.4, H=20.4 and K> 19.3 (3sig) They also report variability of the source at a period consistent with the orbital period of the system. The authors perform SED fitting, and obtain that the Optical/NIR quiescent luminosity can be modeled with a irradiated companion star. Based on this they can deduce a lower limit to the B field of the pulsar, B> 6e7 G. Finally they argue that the only way to obtain the irradiated luminosity they measure, is if the energy is provided by the rotational energy of the NS emitted in the form of a relativistic particle wind. More details can be found in D'avanzo et al. 2007 accepted in A&A | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #220 July 12 2007 |
Kennea and Capitanio 2007
ATel 1140 report the results of Swift observations of
two IGRs, J17091-3624 & J17098-3628.
The authors report refined X-ray position for both sources IGR J17091-3624 lies at: RA = 17h 09m 07.6s Dec = -36d 24' 24.9'' +- 3.6 " @90% confidence which probably rules out the association with a tentative radio counterpart proposed by Rupen et al. and Pandey et al. IGR J17098-3628 lies at RA= 17h 09m 45.9s, Dec = -36d 27' 58.8' +- 3.5" @ 90% confidence. This is 1.8" from previous XRT position and 1.5"from the probable radio counterpart reported by Rupen et al. The spectrum of IGR J17091-3624 is best fitted by an absorbed disk blackbody, with N_H = 0.51e22 cm-2, and kT = 2.1 keV. The 0.2-10 keV unabsorbed flux from the source is ~1e-10erg/s/cm2. Although th high quality of the fit, the author mention that a power law yields a good fit, with parameters similar to those observed in the past during a hard state. IGR J17098-3628 is well fitted by an absorbed disk blackbody model, whith Nh=0.89e22 cm-2 and kT = 0.89. The 0.2-10 keV unabsorbed flux is ~9 E-10 erg/s/cm2 More details in Kennea & Capitanio 2007, ATel 1140 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #219 July 11 2007 |
Degenaar et al., 2007
report on their Chandra observation of the faint XMM/INTEGRAL
transient XMMU J174716.1-281048/IGR J17464-281.
They give a refined position to the source: R.A. = 17h 47m 16.16s Dec = -28¡ 10' 48.0" (+- 0.5 " @90% confidence) The ACIS-S source spectrum is well represented by an absorbed powerlaw model with Nh~9E22 cm-2 Gamma ~2.2. The (2-10 keV) unabsorbed flux is ~3.0E-12 erg/cm2/s. These parameters are similar to what was seen during previous Swift observations. The authors also report results obtained in V, I and H-band images using the SMARTS 1.3m telescope. A faint source coincident with the Chandra position was detected at a S/N-ratio of 4.3 in the H-band image. This suggests that this source is the IR counterpart of XMMU J174716.1-281048. The source was not detected in I or V bands, most likely due to the high Nh in the direction of the source. More details can be found in Degenaar et al. 2007, ATel 1136 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #217 July 10 2007 |
Funk et al., 2007 A&A, 470, 249 report the
results of observation of the high energy source HESS J1813-178
associated to the soft gamma source IGR J18135-1751, X-ray source
AX J1813-178, and to the SNR G12.82-0.02.
Their radio observations show the presence of a giant molecular cloud in the vicinity of the high energy source, but the authors exclude a relation of this cloud to the high energy source, although they mention that it may have influenced its evolution in the past. The X-ray observations allowed them to detect the presence of a compact core with an extended tail at a position coincident with the ASCA source. The refined XMM-Newton position is RA=18h 13m 35.16s DEC=-17d 49' 50.0" +-2", which is 1' away from the best HESS position. The extension is estimated to be 21" in size. From the spectral analysis of those data Funk et al. report the source has an absorbed power law like spectrum with Nh=1e23 cm-2 and Gamma=1.8 which they attribute to a PWN, although they do not detect any pulsation which would clearly be indicative of a pulsar. Comparing the X-ray images with VLA images the authors suggest that the source is a probable composite SNR composed of a PWN (the compact X-ray source) in a shell like radio structure. They further discuss the origin of the very high energy emission, and compare models where either the compact X-ray source or the shell of the SNR are at the origin of the HESS emission. Their results show that either model could explain this emission. More details can be found in Funk et al. 2007, A&A, 470, 249 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #216 July 2 2007 |
in't Zand et al., 2007
A&A 469, 1063
report INTEGRAL and RXTE observations
of IGR J00370+6122.
While using the ASM long term light curve
they can refine the orbital period and
ephemeris to Tmax=53001.7+(I*15.6627) They also find the period while folding the INTEGRAL 20-45 and 45-89 keV light curves. They remark differences in the profiles of the folded light curves, and remark that between peaks the "quiescent level" of the source is at least 11 times fainter than the peak (as seen with INTEGRAL). They also interpret the differences as due to a possible softening of the source in the decay phase of the "outbursts" They also report spectral analysis performed with PCA and ISGRI which shows that the average spectrum during the flare shows Nh~9.1 e22 cm-2 and Gamma=2.14 (PCA), while the ISGRI spectrum is somewhat harder with Gamma=1.84 in't Zand et al. also report the possible detection of a coherent signal at 359s that they associate to the pulsar spin period. Given the pulse period and orbital period, this system lies in the wind accretion regime in the Corbet diagram. More details can be found in in't Zand et al. 2007 A&A 469, 1063 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #216 June 20 2007 | Malizzia et al., 2007 accepted in ApJ Malizzia et al. 2007 accepted for publication in ApJ report the results of Swift observations of a certain number of AGN, including about 25 IGRs. For all sources they give refined position obtained with XRT, as well as spectral parameters they obtain through the fits to the data. Finally they can give identification for most of them, and based on a new diagnostic tool, Nh vs HR(2-10/20-100 keV), they can further identify objects whose identification remains difficult through spectral analysis. I report below the main properties of the sources (position, error, type and redshift when known) More details can be found in Malizia et al. 2007 astro-ph/0706.2547 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #215 June 12 2007 |
Bonnet-Bideau et al., 2007 accepted in A&A
report the identification of IGR J00234+6141
as an intermediate polar from INTEGRAL and
optical observations.
They first give an X-ray refined position of the source at RA=00h 22m 54.3s Dec=+61deg 43' 05" +- 5.2 ' at 90% confidence which confirms the association of IGR with the already proposed Rosat source and Optical counterpart. The ISGRI spectrum is well fitted by a thermal bremsstrahlung with kT=31.3 keV, and the 20-100 keV flux is 8.3E-12 erg/cm2/s From their Optical observations, the authors report the identification of a spin period of 563.5s for the compact object and an orbital period of 4.033 hours. The mean Optical spectrum of the source is typical of magnetic CVs with strong emission lines of the Balmer series, HeII, HeI and CIII-NIII The authors further discuss their results and based on some estimates suggest that the surface magnetic field of the WD is 2.4e5 G which would make the source a low accreting IP with a low B. More details can be found in Bonnet-Bideau et al. astro-ph/0706.1433 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #214 June 11 2007 | Hannikainen et al., 2007 accepted in MNRAS present H- and K-band spectra of IGR J19140+0951 obtained with UKIRT. The IR counterpart was identified by in't Zand et al. (2006) with the heavily reddened 2MASS 19140422+0952577. Nespoli, Fabregat & Mennickent (ATel 983), based on K-band observations alone, estimated the spectral type of the counterpart to be B1 I. In this paper, both K- and H-band spectra are analyzed, rendering the classification more robust. The spectral lines used in the identification were HeI (2.0581 and 2.1126 microns), NIII (2.1155 microns) and HI (Br-gamma at 2.1661 microns) for the K-band spectrum, and the HeI line (1.7002 microns) for the H-band spectrum. Based on these data, the authors confirm the supergiant nature of the star, and tweak the spectral classification to B0.5. Based on the apparent K-magnitude of the star as reported in inÕt Zand et al., and assuming a typical absolute K-magnitude for a B0 supergiant and the corresponding K extinction for IGR J19140+0951, a distance of 5 kpc is estimated. A B0.5 supergiant would place the source slightly closer, supporting the Sagittarius arm location as proposed by in't Zand et al. More details can be found in Hannikainen et al. astro-ph/0706.1129 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #213 June 4 2007 | Chakrabarti et al., 2007 ATel 1096 report on the results of a Chandra pointing on the neutron star XRB IGR J17191-2821. They do not detect any source within 30" from the best position obtained with Swift/XRT. Assumin a power law index 1.71 and Nh=5.7e21 cm-2, they deduce a 2-10 keV source flux of <6.9E-14 erg/cm^2/s (<3.2E-3 mCrab), which implies that the 0.3-10 keV luminosity at the time of the Chandra observation was <1.2E33 ergs/s, assuming the 11 kpc upper limit deduced from previous observations. More details in Chakrabarti et al. 2007 ATel 1096 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #212 May 21 2007 |
Degenaar & Wijnands, 2007 ATel 1078 report the results
of a Swift/XRT observations of the faint transient
IGR J17464-2811/XMMU J174716.1-281048.
The source is clearly detected the source during their observations. By fitting the source spectrum with an absorbed powerlaw model (nH=9.0E22 cm-2, photon index=2.25), theunabsorbed flux is 7.4E-12 erg/cm2/s (2-10 keV) which translates to a luminosity of 1.1E34 erg/s at 3.5 kpc. The authors further discuss the different detection of the source and conclude that the source is a transient system with a quiescent emission at least two orders of magnitude lower than during periods of activity. XMMU J174716.1-281048 can be classified as a very-faint X-ray transient. The fact that the Swift observation detected the flux at a similar one as during the XMM-Newton observations strengthens the suggestion that the system is undergoing a prolonged accretion episode of many years. More details can be found in Degenaar & Wijnands 2007 ATel 1078 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #211 May 17 2007 |
Thompson et al. 2007 (ApJ, 661, 447) report the results
of observations of IGR J17252-3616 (EXO 1722-363).
They refine the orbital period to P=9.7403 days with
data collected over more than 7 years.
The ycan set a limit on the eccentricity to e< 0.19 which shows
it is consistent with being circular.
They also report the observation of a torque reversal
between 1998 and 2006.
The mass function of the system is 11.7 solar masses, which confirms the source is a HMXB. The authors also constrain some parameter of the companion star of the system with a radius of 21 to 37 solar radius and a mass not greater than 22 solar masses. The inclination of the system is greater than 61 degrees. The star is in the range of BO I to B5 I spectral type, and the distance between 5.3 and 8.7 kpc. The spectral analysis reveal a variable Nh and Fe Kalpha lineand photon spectal index. More details in Thompson et al. 2007, ApJ, 661, 447 Klein-Wolt et al. 2007, ATel 1075 report the detcetion of a kHz QPO in the range between 700 and 900 Hz in RXTE observations of IGR J17191-2821. They also mention the detection of an additional kHz QPO at a frequency of ~1030 Hz on several occasions. They identify the latter with the upper kHz QPO and the one at lower frequencies with the lower kHz QPO. The frequency separation is about 330 Hz and is consistent within 3 sigma with the spin frequency as determined from the oscillations seen during the type-I X-ray burst. According to them IGR J17191-2821 behaves during its outburst as a typical neutron star atoll sources in outburst. More details in Klein-Wolt et al ATel 1075 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #210 May 10 2007 |
IGR J17191-2821: Klein-Wolt et al. 2007, ATel 1065 report the observation of an increase of intensity of this source which demostrates a bright outburst. RXTE scans show the source was detected at 2-10 keV level of 30 and 70 mCrab on April 29 and May 2 respectively. The source was detected with Swift XRT at a high level of ~1.2E-9 erg/sec/cm^2 (absorbed 2-10 keV flux). The spectrum is well represented by an absorbed (Nh=5.30 e21 cm-2) power law (Gamma=1.75). The authors also report the observation of a type-I X-ray burst that lasted for about 50 seconds and during which the Swift count rate increased by a factor ~3. The burst spectrum is best fitted with a black body of temperature 0.99 +/- 0.08 keV. Based on the flux from the source they can set an upper limit for the distance of 23 kpc. The author further discuss these properties and argue that it is likely that the source is closer, the observation of a type I burst reveals the compact object is a NS probably in a low mass system. Further to this Markwardt et al. 2007 ATel 1068 (and 1069) mention the detection of this source with RXTE/PCA on 2007 May 4 at a 2-10 keV persistent flux level of about 85 mCrab. They also report the detection of an X-ray burst and high frequency oscillations during the burst. The oscillation frequency drifted from about 292 Hz to 294 Hz. They argue that the neutron star spin frequency is probably near the maximum oscillation frequency, or 294 Hz. Based on the peak flux during the burst they can refine a new distance upper limitof ~11 kpc. Finally Klein Wolt et al. 2007, ATel 1070 report a refined position to this source based on the Swift/XRT data. The best position is : RA= 17h 19m 15.13s Dec=-28d 17' 57.1" (+- ~4"). They estimate a 2-10 keV unabsorbed flux of ~53 mCrab, indicating the source is decaying They obtained V, I and H-band images of the field of IGR J17191-2821 using the SMARTS 1.3m telescope and ANDICAM instrument on May 4.295 UT. They detect two sources at (RA,DEC) = (259.811453,-28.297926) and (259.812253 -28.297579) +- 0.4" within the Swift error circle, in all three bands. Those sources were previsously indetected in USNO B1.0 and 2MASS catalogues. More details in Klein Wolt et al. 2007 ATel 1065 and 1070, and Markwardt et al. 2007 10681069 IGR J16194-2810 Masetti et al. 2007 accepted in A&A report multiwavelength studies of this object. Their Swift/XRT observations allows them to refine the position of the source to RA= 16h 19m 33.29s dec= -28d 07' 40.8" (+- 3.5" @ 90%) They can identify USNO A2.0 U0600-20227091 as the optical counterpart to the X-ray source. Their optical spectrum shows several lines and they identify it as a M2 III star. They can set an upper limit on the distance to the source of 3.2 kpc. The authors discuss their findings, the presence of a M star and the X-ray Swift and INTEGRAL spectra of the source, and clearly identify IGR J16194-2810 as a new symbiotic X-ray binary. The typical X-ray spectral parameters are an absorption column density of Nh= 1.6e21 cm-2, and the spectra are well fitted with a comptt model with kT0=0.63 keV, kTe=7.6 keV, Tau=6.8 which are more typical of a neutron star primary. More details can be found in Masetti et al. 2007 astro-ph 0704.3682 IGR J17254-3257 Chenevez et al. 2007 accepted in A&A report contemporaneous XMM and INTEGRAL observations of IGR J17254-3257. They first refine the X-ray position of the source to RA = 17h 25m 24.8s dec= -32d 57' 15" (+-2") with XMM/pn, and MOS1 With improved position rules out the counterpart suggested by Stephen et al. based on the position of the Rosat object coincident with the IGR source. Due to the relative steadiness and weakness of the long term emission of the source the authors performed a joint INTEGRAL-XMM fits accumulating the data over the entire data sets of both instruments. The source spectra are well represented by an absorbed black body and cut-off power law, with Nh=1.79e22 cm-2, kT=1.06 keV, Gamma=1.64 and Ecut=62 keV They also report the analysis of 2 bursts, which were soft and for which no emission is detected above 20 keV. The first burst is well fitted with a single bb model with kT=1.4keV. For the second (an longer) one they could analyse the peak spectrum and the decay phase. A single bb fits the data well, with teperature decreasing ffrom 1.6 keV to 1.2 keV. Based on the peak luminosity of the burst they can set an upper limit to the distance of 14.5kpc. The authors further discuss their findings in the framework of burst models and mention in particular that while the short burst is typical of type I the second is more unusual and may be pure He ignition. They conclude that the long burst results from the ignition of a large pile of He under a steady H burning shell. The short burst occur when a weak hydrogen flash tirggered a mixed H/He burst. More details in Chenevez et al. 2007 astro-ph 0705.1249 |
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| Mail #209 April 23 2007 |
First Porquet et al. 2007, ATel 1058 report some XMM results
on IGR J17453-2853/GRS 1741.9-2853. The XMM source location is compatible with those of CXOGC J174502.3-285450, AX J1745.0-2855, and GRS 1741.9-2853. They observed 2 X-ray bursts which is consistent with the bursting behaviour of the latter. Since a renewed X-ray activity of this source was reported earlier with Chandra, Swift and INTEGRAL the authors conclude that the outburst duration is at least 7 weeks for this transient. During the last XMM-Newton observation, obtained on April 3-4, 2007, the XMM-Newton/EPIC count rate had decreased by about a factor of 2.5 in less than one day. More details in Porquet et al. 2007 ATel 1058 In addition, Sguera et al. 2007, accepted in A&A report the INTEGRAL/IBIS analysis of the only flare ever detected of IGR J11321-5311. They give arefined position based on the IBIS mosaic. The source lies at RA=11h 32m 15.72s Dec=-53deg 11' 41" (+-1.5' at 90%). The source was active during 3.5 hour and showed a short and bright 1.5 hour flare. the 20-300 keV peak flux is 80 mCrab. The 17-300 keV IBIS spectrum does not show any break up to 300 keV and according to Sguera et al. it can be well represented by a black body of 1 keV with a radius of 7.7 km and a hard power law with photon index 0.55. On a scw basis they see some spectral evolution. The authors discuss the possible type of the emitting object and suggest that it could be an AXP, although firm conclusions cannot be drawn. More details can be found in Sguera et al. 2007, A&A accepted astro-ph 0704.2737 |
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| Mail #208 April 20 2007 |
Del Santo et al. 2007, accepted in A&A
report the analysis
of INTEGRAL observations of the INTEGRAL source
IGR J17464-2811 the probable gamma-ray counterpart to
XMMU J174716.1-281048
They focus on period of bursts seen by JEM X and IBIS. The decay times of 71.6s in the 3-6 keV range vs 7.3s in the 20-25 one, is indicative of a spectral softening typical of type I X-ray bursts. There's also evidence of a double peaked pulse profile which is the signature of Eddington limited burst showing photospheric expansion. Using these arguments and a typical Eddington luminosity for a neutron star they derive a possible distance of 2.8-4.6 kpc, with a prefered value of 3 kpc. The authors re-analyse Chandra and XMM data of the source. They then further discuss their findings in the context of Very faint X-ray transient (a.k.a. burst only sources), a class to which IGR J17464-2811/XMMU J174716.1-281048 belongs. More details in Del Santo et al. 2007 accepted in A&A astro-ph 0704.2134 |
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| Mail #207 April 16 2007 |
Brandt et al. 2007, ATel 1054 report the detection of two X-ray bursts from
IGR J17597-2201 with INTEGRAL/JEM-X.
The bursts were detected on April 6-8 2007 while INTEGRAL was pointing at SGR 1806-20.
They reached a peak flux of about 0.5 Crab in the 3-10 keV
band. The bursts shape are FRED-like with an e-folding time of about 5 seconds. This confirms IGR J17597-2201 is a burst source, as suggested by the partial detection of a burst reported by Markwardt et al. (ATEL #156). According to Brandt et al. the current burst recurrence time could be of 3-10 hours. More details in Brandt et al. 2007, ATel 1054 |
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| Mail #206 April 10 2007 |
After having pointed Swift towards the position of IGR J17394-4638
Miller et al. 2007 report the absence of any X-ray source
within the INTEGRAL error circle.
In a subsequent ATel, they report that in fact this new source is actually
4U 1735-44. The false identification was due to a problem of bad attitude
affecting the near real time data.
This problem being corrected in the processed data, the 4U source is found at its right
place.
Therefore I'll remove IGR J17394-4638 from the web page. All details in Miller et al. 2007 ATel 1052 |
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| Mail #205 April 5 2007 |
Romano et al. 2007,
accepted in A&A, report
the results of a Swift monitoring of the last outburst
of the recurrent SFXT IGR J11215-5952.
Combining all their pointings they refine the
X-ray position of the source to: RA=11h 21m 46.90s Dec=-59deg 51' 46.9" (+-1.1" at 90% confidence) which is 1.2" away from the Optical counterpart. This programme allowed them to monitor the entire outburst, which lasted 23 days. The source (1-10 keV) luminosity was below 3.7e33 erg/s (at a distance of 6.2 kpc) before the outburst and reached 1.1e36 erg/s at maximum. After the outburst the source was fainter than 1.2e33 erg/s Romano et al. mention that the "short outbursts" or flares lasting minutes to hours that led to the definition of SFXT are actually part of a longer outburst episode that was missed in most sources due to observations with lower sensitivity instruments. Those flares may be due to episodic accretion from the massive wind of the companion, while the ouburst itself is due to the accretion near the periastron passage. They further mention that the source showed a hard spectrum at the maximum of the outburst, that softened as the source flux was decaying. More details and results from the spectral fits can be found in Romano et al. 2007 accepted in A&A astro ph 0704.0543 |
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| Mail #204 March 30 2007 |
Leyder et al. 2007,
A&A, 465, L35 report additional
analysis of the INTEGRAL, Swift and Optical observations of
IGR J08408-4503 (see Gotz et al. 2007; Kennea and Campana
2006; Masetti et al. 2006, Mereghetti et al. 2006).
In addition to what reported earlier, their
INTEGRAL ISGRI/JEM-X spectra are well represented by a broken power law
or a comptt with a break energy of 14 keV for the former, and
an electron temperature of 7 keV and optical depth 4 for the
latter. They report a refined position based on the Swift/XRT observations. The source lies at RA= 08h 40m 47s Dec= -45deg 03' 32" (+-4.1" @ 90%) The authors report a 2-10 keV flux of 3.4e-13 erg/cm2/s but mention that most of the detected counts have an energy smaller than 1.5 keV From several arguments on the Optical counterpart they estimate a distance to the source of 2.7 kpc. They then discuss the probable type of the source and also come to the conclusion that IGR J08408-4503 is a SFXT (Gotz et al. 2006, 2007; Masetti et al. 2006; Barba et al. 2006). Based on the type of the Optical counterpart and the X-ray luminosity, they estimate an orbital separation of > 1e13 cm, and they thus suggest that the main difference between SFXT and persistent HXMB may be due to difference of orbital radius. More details in Leyder et al. 2007, A&A, 465, L35 |
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| Mail #203 March 29 2007 | Masetti et al. 2007, ATel 1034, report the identification of 2 INTEGRAL sources through a refinement of their X-ray position and identification of the Optical counterparts IGR J15539-6142: According to Masetti et al. only the nucleus of ESO 136-6 emits X-rays detected by Swift (the position is not given), which makes it the most reliable counterpart candidate to the IGR source. The Optical spectra show narrow Halpha, [NII] and [SII] emissions at redshift z = 0.015. Line ratios are consistent with those of a Seyfert 2 AGN. IGR J16500-3307: Only one soft X-ray source can be found in the INTEGRAL error box (a Rosat source see Stephen et al. 2006), and the Swift XRT allowed Masetti to refine the error box to 3.4" (X-ray position still not given). There is only one Optical object compatible with the X-ray source: U0525_24170526 located at RA = 16 49 55.64 and Dec = -33 07 01.8 The optical spectrum shows Halpha, Hbeta, HeI and HeII emissions at z = 0, which indicates that this is a Galactic object. Masetti et al. conclude to a Cataclysmic Variable or a Low-Mass X-ray Binary. More details in Masetti et al. 2007 ATel 1034 ATel 1034 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #202 March 27 2007 | Masetti et al. 2007, ATel 1033, report Optical identification of the "putative" counterpart to newly discovered IGRs. They identify 1RXS J061148.5-662430 as the most likely counterpart to an INTEGRAL source first identified as PKS 0611-663. The spectrum of USNO-A2.0 object U0225_02842370 (RA = 06 11 48.32, Dec = -66 24 34.0), which is the only optical source in error circle of the ROSAT source, shows broad Balmer and narrow [OIII] emission lines at redshift z = 0.230. They identify this object as a Seyfert 1.5 AGN Masetti et al. add that the rosat and USNO sources are not associated with the PKS source, and suggest to rename the hard X-ray source IGR J06117-6625 IGR J07437-5137: the optical spectrum of galaxy LEDA 21656, at z = 0.025 shows narrow Halpha, [NII], and [OII] emission lines. The Halpha/[NII] line ratio is consistent with that of Seyfert 2 AGNs. IGR J14561-3738: the spectrum of galaxy LEDA 53392, at redshift z = 0.025 shows Halpha, [NII] and [SII] in emission. Line ratios are consistent with those of Seyfert 2 AGNs. IGR J16056-6110: The galaxy LEDA 3079933 is within the 8" radius error box of ROSAT source 1RXS J160551.9-611142. The spectrum shows broad Balmer and narrow [OIII] emissions at redshift z = 0.025. Line width and ratios allow them to identify this source as a Seyfert 1.5 AGN. More details can be found in Masetti et al. 2007 ATel 1033 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #201 March 12 2007 |
Klein-Wolt et al. 2007,
ATel 1025 report on Swift follow up
observations of the INTEGRAL source IGR J17191-2821.
Their pointings do not show a source within the INTEGRAL error circle with an upper limit of 0.0021 cnts/s. This translates into an 2-10 keV unabsorbed flux of 8.7*10E-14 erg/s/cm^2 or 0.004 mCrab with a Gamma=1.8 and Nh=3.4e21 cm-2. In the first pointing they detect a source at distance of about 3.5 arcminutes from the best (INTEGRAL) position of IGR J17191-2821 at: RA= 259.8114 Dec= -28.3005 (+- 9.1"). The flux is 3.6*10E-13 erg/s/cm^2 (unasorbed) or 0.02 mCrab (assuming the same Nh and photon index as before). The source is not visible any more in the following pointing. The author add that although the formal INTEGRAL error circle on the position of IGR J17191-2821 may indicate that the sources are unrelated they, however, consider it still a small possibility that both sources are one and the same since offset between positions have happened in the past Whether the IGR was detected by Swift or not, over the span of 5 days (from March 3 to March 8) IGR J17191-2821 has decreased by a factor 500 or more. More details in Klein-Wolt et al. 2007 ATel 1025 |
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| Mail #200 March 8 2007 | Swank et al. 2007, ATel 1022 report the results of an RXTE scan of the region containing the new INTEGRAL source IGR J17191-2821. A source whose position is coincident with that of the IGR was detected with a 2-10 keV flux of 10 mCrab. The authors report that in a following observation nothing was detected and they measure a flux of < 0.5 mCrab which is approximately the flux from the Galactic Bulge before the source was detected. The source was not detected the following day either, and no flares brighter than 2 mCrab were seen in a reanalysis of all scans from this region since 1999, Feb 5. The authors further discuss the type of object and mention that the only certainties about it is the maximum duration of 1.7d of its activity and its hard spectrum. All this binary could indicate IGR J17191-2821 is a binary with a compact object and a high mass companion. Although, Swank et al. indicate that a low-mass companion cannot be excluded, they add that it then had a very short outburst and an unusually hard spectrum. A stellar flare from a near-by star or an outburst from a magnetar cannot be ruled out either. More details in Swank et al. 2007 ATel 1022 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #199 March 6 2007 |
Tuerler et al. 2007, ATel 1021 report the discovery of a new source
IGR J17191-2821with ISGRI, during a Key Programme observation
of the Galactic Bulge.
The source is located at RA= 17h 19m 04s Dec= -28d 21' 00" (+-2.5 arcmin) It has a 20-40 keV flux of ~9mCrab is detected in a mosaic of the whole observation but not in individual pointings. It is marginally detected in the 40-80 keV range with a flux of 5.8 mCrab. The authors mention the presence of 2 nearby sources from the Simbad database 1RXS J171909.4-282041 (at 1.4') and IRAS 17159-2819 (@ 1.6'). They further indicate the presence of the unidentified EGRET source 3EG J1717-2737 located at RA=17h 17m 12s, dec=-27deg 37' 48" (+-0.64 deg @95% confidence). More details in Tuerler et al. 2007 ATel 1021 |
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| Mail #198 March 5 2007 | In an article accepted for publication in A&A, we (Bodaghee et al., 2007) describe the parameters of IGR sources with respect to those of previously known sources detected by ISGRI. The catalog of source parameters includes references for X-ray absorption (nH) values, pulse and orbital periods, distances or redshifts, object class, and the most precise position known for all 214 IGR sources detected so far. IGRs that have been classified are mostly extragalactic (50 = 23%), followed by Galactic X-ray binaries (38 = 18%), and miscellaneous Galactic sources such as CVs, SNRs, etc. (15 = 7%). A majority of IGRs remain unclassified (111 = 52%). Their spatial distribution suggests a Galactic population composed primarily of LMXBs. Almost all of them have transient X-ray emission which favors LMXBs rather than AGN behind the Galactic plane. If many of the unclassified IGRs are, in fact, LMXBs, then some of the reasons why they have avoided classification are: the optical counterparts of LMXBs tend to be faint; their location in the Galactic bulge and plane where obscuring dust and source confusion make it difficult to identify an optical counterpart; and their X-ray emission is often transient thereby hindering follow-up observations. It is interesting to note that only 6 (3%) IGRs have been classified as a LMXB. Thanks to multiple ToO campaigns targeting IGRs, half of them were classified within the last year. On average, IGRs are more absorbed (by a factor of ~4) and they tend to have longer pulsation periods (~1 ks) than sources that were previously known. For the most part, these attributes are due to an influx of new members to the growing class of HMXBs with supergiant companions. The distribution of orbital periods of IGRs follows the bimodal trend set by previously-known sources, i.e. a peak at short orbital periods (CVs, LMXBs) and a peak at long orbital periods (HMXBs). Nearly all of the IGR HMXBs for which both spin and orbital periods have been measured are situated among other wind-fed accretors in a Corbet diagram. Plots of nH versus the spin (Ps) or orbital period (Po) show that HMXBs are generally segregated into distinct regions of the diagrams depending on whether the stellar companion is an OB supergiant star or a Be star. Furthermore, the nH and Ps are weakly correlated, while the nH and Po are weakly anti-correlated. These plots could help to assign OB supergiants or Be stars to HMXBs whose companions are still unidentified. For example, IGR J16358-4726 and IGR J19150-0451 are likely to host OB supergiant companions based on their location in the nH-Ps and nH-Po diagrams, respectively. For more results, including the table of the relevant parameters of IGRs and ISGRI-detected sources in general, and a discussion of the effects of Galactic rotation on the distribution of HMXBs, please read Bodaghee et al. (2007): astro-ph/0703043 In addition, Türler et al. 2007 (ATel 1019) report the observation of a bright outburst from the supergiant fast X-ray transient XTE J1739-302 = IGR J17391-3021, one of the brightest ever detected for this source. The event started on March 2, 2007 at about 13:30 UT, reached a maximum after an hour and faded over 0.5 to 1 hour. The source reached a maximum of 330 mCrab in the 20-40 keV band and 250 mCrab in the 40-80 keV band. No other strong activity of the source was seen several hours before and after the outburst. The authors also report some spectral analysis at the moment the source was the brightest. A thermal bremmstrahlung model or a cut-off powerlaw represents the 20-100 keV spectrum well, while single powerlaw or a blackbody model do not. The bremsstrahlung has a temperature kT ~ 22.5 keV. An INTEGRAL light curve can be found at: light curve of IGR J17391-3021 while more details can be found in Türler et al. 2007 (ATel 1019): ATel 1019 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #197 March 2 2007 |
Tomsick et al. 2007 ATel 1018 report on the results
of a Chandra observation of IGR J09026-4812.
The refine the X-ray position to the source to: R.A. = 09h 02m 37s.29 Decl. = -48d 13' 34".2 (+-0.6" @90% confidence) Although the spectral analysis is somewhat complicated by instrumental pile-up, the spectrum is well represented by an absorbed power-law model with a flux of 5 x 10^-12 ergs/cm^2/s (0.3-10 keV, absorbed). Preliminary results give N_H = 2.2x 10^22 cm^-2 and Gamma 2.7. The authors identify 2MASS J09023731-4813339 that lies 0".4 from the Chandra position as the likely IR counterpart. They report IR magnitudes of J = 15.57+/-0.08, H = 13.86+/-0.07, and K = 12.69+/-0.04. Tomsick and collaborators further discuss the type of the system and suggest, in particular because of the bright IR counterpart, that it is a HMXB. More details in Tomsick et al. 2007 ATel 1018 |
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| Mail #196 February 27 2007 |
Muno et al. 2007 ATel 1013
report on Chandra observations of GRS 1741.9-2853.
They refine the position to
17h 45m 2.34s
-28o 54' 49.9"
(+-0.5")
The Chandra spectrum although affected by pile up is well represented
by a Gamma=0.9 power law absorbed by N_H=9.0e22 cm^-2.
The observed 2-8 keV flux (corrected for pile-up) was 3e-11 erg cm-2 s-1, which, assuming a distance of 8 kpc, leads to an estimated intrinsic 2-8 keV luminosity of 4e35 erg s-1. The authors further discuss their results and report that the association of GRS 1741.9-2853 and the INTEGRAL source IGR J1745-2853 further supports the Swift association of both sources. More details can be found in Muno et al. 2007 ATel 1013 |
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| Mail #195 February 23 2007 |
Kuulkers et al. 2007 ATel 1008, suggest that IGR J17453-2853 and
GRS 1741.9-2853 may be the same source.
Although the statistical 90% error box of each seem to argue against
this association, the authors mention that the Granat source was
the only active source in the immediate vicinity of the INTEGRAL source
seen by Swift a day after the first mention of renewed activity of IGR J17453-2853.
In addition combining their data, they found a source with JEM X at RA, Dec (degrees, J2000.0) = 266.265, -28.92, (+-2 arcmin), hence consistent with the position of the Granat source. Kuulkers and collaborators further argue that the Swift spectrum of GRS 1741.9-2853 is consistent with the 20-60 keV flux measured with INTEGRAL. They also mention that both sources were active at the same time in April 2005. Thus their conclusions, although they clearly say that they cannot exclude the possibility of two sources being active at the same time (but they consider this possibility unlikely). More details can be found in Kuulkers et al. 2007 ATel 1008 |
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| Mail #194 February 20 2007 |
Sguera et al. 2007 (accepted for publication in A&A) report on several
observations of IGR J18483-0311 with INTEGRAL and Swift.
They identify 5 new outbursts of the source in all INTEGRAL archival data, only one of which is simultaneously in the JEM-X and IBIS fov, allowing thus a brand band spectrum to be studied. This 3-50 keV spectrum is well represented by an absorbed cut-off power law with Nh=9e22 cm-2, Gamma=1.4 and a cut off energy of 22 keV. The authors also mention that an absorbed bremsstrahlung provides a good fit to the data with Nh=7.5e22 cm-2 and kT=21.5 keV. In all the other cases fits to the 20-60 spectra are well represented with bremsstrahlung of temperatures of similar temperatures for the 5 outbursts. The timing analysis of these data yielded the discovery of a period of 18.52+-0.01 days interpreted as the orbital period of the system, and a pulse period (from the JEM-X data) of 21.0526+-0.0005s with a pulse fraction of 65+-10%. The Swift observations allowed Sguera et al. to refine the position of the source to RA=18h 48m 17.17s Dec=-03deg 10' 15.54" +- 3.3" The swift spectra are well represented by absorbed power laws with Gamma=1.7 and 1.3 and Nh = 6.3e22 and 4.8e22 for the 1st and 2nd observation repsectively. The authors mention, however, that if Nh is frozen to the average value of 5.5e22 cm-2 no spectral evolution is seen between these 2 obs. The Swift refined position allowed them to identify an Optical counterpart from the USNO-B1.0 catalogue located at RA=18h 48m 17.2s Dec=-03deg 10' 16.5" with magnitudes R=19.26, I=15.32, J=10.74, H=9.29, K=8.46. The authors discuss all these results, and first conclude that the source contains a pulsar with a spin period of 21.0526s, while the highly redenned Optical counterpart suggest by analogy with other such systems the source is a HMXB. They further argue that the source is a likely Be system by the position it lies in a Corbet diagram, but they can't rule out a SFXT, although the typical ratio between max and min luminosity they observe here is at least 10 times lower than that of typical SFXT. More details can be found in Sguera et al. 2007 accepted in A&A, astro ph 0702477 |
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| Mail #193 February 19 2007 |
Kuulkers et al. 2007, ATel 1005
report that the transient
IGR J17453-2853 was active during their first observation
of their Galactic bulge monitoring, performed between
Feb 15 18:35 and 22:17 UTC.
The IBIS/ISGRI 20-60 keV flux was about 11 mCrab, while it is not detected in the JEM-X bands with upper limits of about 5 mCrab in 3-10 and 10-25 keV. According to them, if the non-detection with JEM-X is due to absorption in the line of sight, N_H should be larger than about 10^23 cm-2. More details can be found in Kuulkers et al. 2007 ATel 1005 |
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| Mail #192 February 15 2007 |
Torres et al. 2007, ATel 1002, report follow-up NIR
observations of the X-ray transient and BHC IGR J17497-2821.
The Ks=15.9 candidate already suggested in previous reports appeared blended with a brighter nearby NIR source to the east which partially overlaps the 0.6 arscec Chandra error circle. The last set of observations discussed by the authors show that the proposed counterpart candidate has faded significantly and is no longer detected with a 3-sigma upper limit magnitude of Ks > 17.8, which is consistent with a late-type companion at a typical distance of the Galactic center. Torres et al. conclude that this large decrease in brightness as compared to the the times when the transient was in outburst confirms that the candidate reported in previous reports (e.g. ATEL #909) is the NIR counterpart to IGR J17497-2821. More details can be found in Torres et al. 2007 ATel 1002 while a finding chart can be found at http://hea-www.harvard.edu/~mtorres/IGRJ17497m2821.html (courtesy M. Torres) |
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| Mail #191 February 12 2007 |
Swank et al. 2007, ATel 999, report the results of RXTE pointed observations
to the fast X-ray transient IGR J11215-5952.
They mention a clear detection starting from Feb 9, and report that they detect pulsation at 186.78s (+-0.3s). The source was faint the following day, although the pulsations could still be detected. The source spectrum is typical of that of a pulsar (power law with a high energy cutoff) The best value for the power law when the pulses were present was 1.07+-0.08, with a cutoff starting at 5.8 +-0.7 keV and an e-folding energy of 15 +-2 keV. The column density was fixed to the value found with Swift. The authors add that RXTE will monitor the source for 3 more days. Light curves are available at http://scipp.ucsc.edu/~dsmith/atel/atel0999/ while more details can be found in Swank et al. 2007 ATel 999 |
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| Mail #190 February 10 2007 |
Sidoli et al. 2007, ATel 997,
analysing Swift/XRT data of the
monitoring of the new outburst of the supergiant fast
X-ray transient IGR J11215-5952, confirm the pulsation
at 180.4 +/- 1 s previously suggested from RXTE data
of the previous outburst of the source.
They also mention existence of an XMM observation of the source and a forthcoming INTEGRAL ToO on this source All details in Sidoli et al. 2007 ATel 997 |
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| Mail #189 February 9 2007 |
Landi et al. 2007, ATel 990, 991 and 992 report the following
results
IGR J14175-4641: refinement of the position with XRT to RA(J2000) = 14h17m03.8s Dec(J2000) = -46d41m39.7s, +- 10 arcsec This allows the authors to confirm the association with the Seyfert 2 galaxy LEDA 511869 at z =0.076. The 2-10 keV XRT flux of 5.8 e-14 erg/cm2/s, and the 20-100 keV IBIS flux of 3.9e-11 erg/cm2/s may suggest the source is a Compton thick AGN. IGR J14552-5133: refinement of the position with XRT to RA(J2000) = 14h55m17.93s, Dec(J2000) = -51d34m13.27s, +- 3.32 arcsec Which confirms the association with the Narrow Line Seyfert 1 galaxy WKK4438 at z = 0.016 The spectrum is power law like modified by low absorption (Gamma = 2.06 and NH = 1.2 e21cm-2) with a 2-10 keV flux of 9 e-12erg cm-2 s-1 IGR J16351-5806 refinement of the position to RA(J2000) = 16h35m13.17s, Dec(J2000) = -58d04m49.68s, +- 5.1 arcsec Which confirms the association with the Seyfert 2 galaxy ESO 137-34 at z =0.009. The X-ray spectrum is an unabsorbed steep (Gamma = 2.3) power law with a 2-10 keV flux of 2.4 e-13 erg cm-2 s-1 More details can be found in ATel 990 In the case of IGR J10043-8702, IGR J10500-6410, IGR J05319-6601 and IGR J11321-5311 the same authors report the non detection of the sources they do not detect any X-ray source around the INTEGRAL uncertainty circle either, except around IGR J05319-6601, around which the High mass X-ray binary RX J0531.2-6609 (at 7.5' from the INTEGRAL position) is detected. More details in ATel 991 Finally, they also report in a following ATel the non detections of IGR J11567+3700, IGR J12488+3315, IGR J13371+1520 and IGR J13103+2001. Arguing that none of the above excesses has been reported in the literature afterwards (including the IBIS catalogs ) they conclude that these sources are probably spurious detections. More details in ATel 992 IGRJ11215-5952: P. Romano et al. mention the detection of the 5th outburst of this source with Swift. A clear renewed flaring activity is observed starting on February 7-8 when the source was observed with a signal to noise ratio of 2.93, after 328 days from the latest outburst. This confirms the periodicity of the outbursts More details can be found in ATel 994 Concerning the same source, Mangano et al. report the observation of a bright flares during subsequent pointings of the source with Swift. The peak of the flare reached ~ 2E-10 erg/cm2/s (1-10 keV) The spectrum can be fitted with a single absorbed power-law with a photon index of 0.93, with Nh~1.02E22 cm^-2. More details can be found in ATel 995 while a light curve of the source can be accessed at http://www.iasf-milano.inaf.it/~sidoli/www/igrj11215/swift_curve.html and through ATel 996 |
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| Mail #188 February 6 2007 |
Sodli et al. 2007,
ATel 987 report the discovery of a new
source IGR J16558-4150 with the IBIS (ISGRI) telescope onboard
INTEGRAL during ToO observations of the black hole
GX 339-4. The ISGRI coordinates are: RA = 16h 55m 48s DEC = -41deg 49' 48" (+- 3'). The average 20-40 keV flux was ~ 8 mCrab. It is not detected in individual 2.6 ksec pointings which indicates no strong variability. The source is not detected in the mosaic image at higher energies, with an upper limit of 4 mCrab in the 40-80 keV band, it is neither detected between 3-30 keV with an upper limit of ~15 mCrab. The authors also mention the existence of the IR source IRAS 16520-4146 at 2.6 arcmin from the best position and that of XMMU J165520.0-41485, at a distance of 5.3 arcmin. More details in Soldi et al. 2007 ATel 987 |
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| Mail #187 February 1 2007 |
Paizis et al. 2007, accepted in ApJL,
report on a Chandra grating observation of the recently
discovered IGR J17497-2821.
The authors extract the most precise X-ray position currently available alpha=17h 49m 38.037s, delta=-28d 21' 17.37" (90% uncertainty of 0.6"). The X-ray spectrum can be well fit by an absorbed (Nh=5.6e22 cm-2) power-law (gamma=1.5) and a disk emission with kTin=0.2 keV. Based on their X-ray position, they also report on optical and near infra-red photometric follow-up observations (mag Ks=16). With the multi-wavelength information at hand, they discuss the possible nature of the source proposing that it is a LMXB, most likely hosting a black hole, with a red giant K-type companion. Should the red giant K-type companion be confirmed, this would make IGR J17497-2821 the first "symbiotic" LMXB hosting a black hole. More details can be found in Paizis et al. 2007, accepted in ApJL, astro ph 0611344 |
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| Mail #186 January 30 2007 |
Nespoli et al. 2007 ATel 983 report the results of their
K-band spectroscopic observations of two IGRs,
namely IGR J18410-0535 (AX J1841.0-0536) and J19140+0951.
IGR J18410-0535: The authors report the presence of HeI, NIII/CIII, and CIV in emission (weak for the later), and HeI and Br-gamma in absorption. These signatures are characteristic of a mid to late O type supergiant. But the authors further argue that the very weak or absent HeII line and the presence of HeI indicate a spectral type not earlier than O9-B0. According to their analysis the estimated spectral type is B0I. IGR J19140+0951: from the presence of HeI and NIII/CIII in emission (weak for the later), and HeI and Br-gamma in absorption plus the absence of HeII, the authors estimated that the spectral type of the companion is a B1I making IGR J19140+0951 a supergiant X-ray binary More details in Nespoli et al. 2007 ATel 983 |
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| Mail #185 January 24 2007 |
The 3rd ISGRI catalogue
by Bird et al. has been accepted for publication in the
Astrophysical Journal Supplement.
It contains information about most of the sources detected by ISGRI, and mention in particular the existence of about 60 new sources. All details can be found in Bird et al. 2007 accepted in ApJS astro ph 0611493 |
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| Mail #184 January 15 2007 |
Linares et al. 2007, accepted in ApJ, report the results
of the timing analysis of the RXTE data of IGR J00291+5934
over the 2004 outburst.
While they first mention that the overall shape of the power
density spectra is typical of low luminosity and hard spectral
state of Atoll sources (ie flat top noise, below a break frequency,
3 broad lorentzians to account for features at Nu> Nu break, and
2 LF QPOs), they remark that the overall 0.1-100 Hz fractional
rms amplitude is very high (42-58 %), the break frequency
is 2 order of magnitude below that usually observed for Z sources
and 1 order of mag below that of Atoll sources.
They also observe that there is no significant power at frequencies > 100 Hz.
All these characteristics are exceptional for NS/LMXBs and are on the contrary comparable to what is seen in BH systems. The authors discuss these findings and mention in particular that the lack of variability above 100 Hz may be due to the combination of the strong magnetic field, and the fast spin of the source which could prevent the accretion disc to reach the innermost regions, place where the highest frequencies are present. Some caution is, however, expressed. One of the main conclusion is that these results refute a simple mass-frequency relation for the variability components of LMXBs. More details can be found in Linares et al. 2007 accepted for publication in ApJ, astro-ph 0609685 |
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| Mail #183 January 10 2007 |
Kuulkers et al. 2007, accepted in A&A, report the results of their
INTEGRAL monitoring campaign of the Galactic bulge.
They first report the detection of a number of new sources , some of which
were previously advertised through ATel.
-IGR J17453-2853 is located at RA= 17h 45m 18s dec= -28° 53' 27" +-2' at 90% It was first found at a flux of 6 mcrab in the 20-60 keV band, and is not detected in the JEM X data, which could indicate high intrinsic absorption, or a source that underwent a hard X-ray outburst. Is peak flux was 27 mcrab, and the source spectrum can be described by a powerlaw with index 2.2. The authors mention that the non detection by JEM X, if due to absorption, implies Nh>1e23 cm-2 -IGR J17454-2703 is located at RA= 17h 45m 19s dec= -27° 02' 20" +-1' at 90% This source was found with JEM X. It reached on one occasion a peak flux of 82 mcrab and 29 mcrab between 3-10 keV and 10-25 keV respectively. The source spectrum is well represented by an absorbed powerlaw with Nh=1.2 e23 cm-2 and Gamma=3.5. -IGR J17456-2901b RA= 17h 45m 39s dec= -29° 01' 44" +-2' at 90% The detection of this source follows the report of a detection of a new source by Swift. Although the authors previously associated this source with the Swift source, they mention that many sources encompass the JEM X error circle, and that the most of their hard X-ray detected emission may come from IGR J17456-2901, while the soft emission does not. Hence the probable existence of a new source which they cannot confidently associate with the Swift source. IGR J17536-2339 and J17541-2252 are two close by source (0.8 degrees). Their hard fluxes are respectively 11 and 10 mcrab in the 20-60 keV band. They lie at: RA= 17h 53m 38s dec= -23¡ 39' 14" +-4' at 90% and RA= 17h 54m 04s dec= -22° 52' 15" +-4' at 90% The former one is positionnaly coincident with the X-ray burster SaX J1753.5-2349 IGR J17354-3255 lies at : RA= 17h 35m 25s dec= -32° 55' 19" +-4' at 90% The source peaked at a 20-60 keV flux of 20 mcrab Concerning other known IGRs, Kuulkers and collaborator mention the steadiness of the proposed Optical counterpart to IGR J17544-2619 (2MASS J17542527-2619526) seen with the Optical Monitor. While at X-ray energies they report parameters for some of the IGRs lying in this field (J17544-2619, J17098-3628, J17252-3616). (Much) More details can be found in Kuulkers et al. 2007 astro-ph 0701244 Note that the quick look and consolidated results of this monitoring are always available at http://isdc.unige.ch/Science/BULGE/ |
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| Mail #182 December 22 2006 |
Brandt et al. (2006, ATel 970)
report the detection of a new source IGR J17464-2811
in archival data of INTEGRAL with the JEM X detectors.
The source was detected on March 22, 2005, at 7h55m03 s while
undergoing a probable type I X-ray burst.
The position of the source from the 3-30 keV energy range is RA = 266.810 deg, DEC = -28.185 deg, (+- 1 arcmin @ 90%). The burst is FRED like in the 3-8 keV range with a time constant of about 70 seconds. In the 8-30 keV band the burst showed a gradual rise over 25 seconds followed by an exponential decay with a time constant of about 30 seconds. The authors interpret this as due to a spectral softening that is a characteristic of Type-I X-ray bursts. The peak flux was 1.0 Crab in the JEM-X 3-30 keV band. The burst was also clearly detected and localized with ISGRI up to 30 keV In a following ATel R. Wijnands 2006 (ATel 972) report that the position of the INTEGRAL source is consistent with that of XMMU J174716.1-281048 R. Wijnands gives further arguments in favour of the association of the 2 sources: the closeness in time of the INTEGRAL and XMM-Newton observations. The XMM-Newton position of this source is RA = 266.817367 deg, Dec = -28.180065 deg (+-~4 arcseconds). R. wijnands also mentions occurences of other bursts seen with XMM and mentions that the transient nature of the source combined with the type-I X-ray burst seen with INTEGRAL suggest that IGR J17464-2811/XMMU J174716.1-281048 is a transiently accreting neutron-star X-ray binary likely in an LMXB. More details in Brandt et al. 2006 ATel 970 Wijnands 2006 ATel 972 |
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| Mail #181 December 18 2006 |
Gotz et al. (2007, accepted in ApJ Letters)
report the discovery of a new Supergiant Fast X-ray transient,
IGR J08408-4503. This source was discovered by INTEGRAL on May 15, 2006, during a bright flare. The source shows sporadic recurrent short bright flares, reaching a peak luminosity of 10 e36 erg s-1 within less than one hour. The companion star is HD 74194, an Ob5Ib(f) supergiant star located at 3 kpc in the Vela region. Gotz and collaborator also analyse the light curves and broad-band spectra (0.1-200 keV) of all the three flares of IGR J08408-4503 detected up to now (based on INTEGRAL and Swift data). The flare spectra are well described by a power-law model with a high energy cut-off at ~15 keV. The absorption column density during the flares was found to be ~10^21 cm^-2, indicating a very low matter density around the compact object. Using the supergiant donor star parameters, the wind accretion conditions imply an orbital period of the order of one year, a spin period of the order of hours and a magnetic field of the order of 10^13 G. More details can be found in Gotz et al. 2007 accepted for publication in ApJ Letters astro-ph 0612437 |
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| Mail #180 December 15 2006 |
Rodriguez et al. (2007, accepted in ApJ Letters)
report the results
of observations of IGR J17497-2821 with RXTE and at radio wavelengths with ATCA.
Our 3~200 keV spectral analysis shows very little variations over a period of 10 days around the maximum of the outburst. IGR J17497-2821 is found in a typical Low Hard State of X-ray binaries, that we either fitted with an absorbed power law with a high energy cut-off, or a more physical model of (absorbed) Comptonization with Nh~3.3-4e22 cm-2, kT~35-40 keV and Tau~1.6-2. In all cases an iron edge at about 6.6-7.1 keV is needed in the fits. The timing analysis shows no particular features, while the shape of the power density spectra is also typical of LHS of XRBs (flat top noise + ~power law decay above, that we represented by the sum of 3 Lorentzians) with ~36% RMS variability. We derived 3-sigma upper limits of 2% on the presence of a 2Hz FWHM QPO. We calculated 3 sigma upper limits ranging from 2.4% to 0.9% on the presence of coherent pulsations between 4mHz and 4096 Hz. No radio counterpart is found down to a limit of 0.21 mJy at 4.80 GHz and 8.64 GHz. We discuss our results and compare the properties of IGR J17497-2821 with those of other sources. Although the position of IGR J17497-2821 in the radio to X-ray flux diagram is well below the correlation usually observed in the LHS of black holes, its X-ray spectral properties make it black hole candidate. More details can be found in Rodriguez et al. 2007 accepted for publication in ApJ Letters astro-ph 0611341 |
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| Mail #179 December 8 2006 |
Tomsick et al. (2006)
report the results of their Chandra observation
of IGR J06074+2205.
They first refine the X-ray position to R.A.= 06h 07m 26s.62 Decl. = +22d 05' 47".6 (+-0.6 ") This allows them to identify a Be star as the counterpart to the X-ray source making the system a Be/X-ray binary. The association between the X-ray source and the INTEGRAL one is strenghtens by the very hard spectrum obtained with Chandra. It ios well described by an absiorbed powerlaw with N_H = (6+/-2) x 10^22 cm^-2 and Gamma=1.3+/-0.8 (90% confidence errors). The absorbed 0.3-10 keV flux of the source is 2 x 10^-12 ergs/cm^2/s. More results can be found in Tomsick et al. 2006 ATel 959 |
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| Mail #178 December 5 2006 |
Masetti et al. (2006)
report on the results of sectroscopic observation
at Optical wavelengths on 4 unidentified IGRs for which a single NVSS radio
source is found in the IBIS error circle.
IGR J00040+7020: the error box include NVSS J000402+701916, which is associated with 2MASX J00040192+7019185. The authors report the presence of Halpha, Hbeta, [OIII], [OI], [NII] and [SII] narrow emissions at redshift z = 0.096 in the Optical spectra. They conclude the object is a Seyfert 2 AGN. IGR J02504+5443 (<=> IGR J02501+5440), the error box encompasses the radio-emitting galaxy LEDA 166445, also an IRAS mid-infrared source. The Optical spectrum is a reddened continuum with Halpha, [OIII], [NII] and [SII] narrow emission lines at redshift z = 0.015. The authors conclude the object is a Seyfert 2 AGN. IGR J15161-3827 LEDA 2816946 can be found in the INTEGRAL error box. The optical source a displays Halpha, Hbeta, Hgamma, [OIII], [NII] and [SII] narrow emission lines at redshift z = 0.036500. The authors conclude it is a borderline source between a LINER and a Seyfert 2 AGN. IGR J16385-2057 the error box include the galaxy Oph J163830-2055, consistent with a NVSS, an IRAS object and with the ROSAT bright X-ray source 1RXS J163830.9-205520. The Optical spectrum shows broad Halpha, Hbeta, Hgamma and Hdelta plus narrow [OIII] lines, all in emission; the redshift of the source is z = 0.026879. The authors classify this object as a Narrow-Line Seyfert 1 AGN. Apart from the last one, for which the presence of the Rosat source gives a more accurate position and strenghtens the association between the different objects, the authors warn that for all object the proposed associations need confirmation through refinement of the X-ray position with arcsec accuracy. More results can be found in Masetti et al. 2006 ATel 957 |
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| Mail #177 November 28 2006 |
Walter et al. (2006, accepted in A&A) report results on IGR J17497-2821 obtained
with INTEGRAL, Swift and at Optical wavelengths.
Based on the variability of a candidate IR/Optical counterpart, the authors propose an association of a source located at RA=17h 49m 38.11s Dec=-28¡ 21' 17.2" with the X-ray source Searching through the X-ray and soft gamma ray data, the authors mention that they do not find any Tipe I X-ray burst in 995 ks of data down to 0.1-0.2 Ledd. The spectrum is well represented by a power law with a high energy cut-off (Gamma=1.67), or a comptonised spectrum, with kT=35 keV and Tau= 1.45 although the temperature of the electron is very poorly constrained. The authors discuss their findings and suggest IGR J17497-2821 is a new X ray nova harbouring a black hole. More details in Walter et al. (forthcoming letter in A&A) preprint (restricted access) |
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| Mail #176 November 17 2006 |
Landi et al. (2006) ATel 945 report the observation of 2 INTEGRAL sources
with Swit XRT. This allows them to 1st refine the X-ray position of the sources IGR J18244-5622 is located at RA = 18 24 19.49, Dec = -56 22 08.72 (+-4.4") This confirms the previously proposed association with the Sey2 galaxy IC 4709 at z=0.017. The X-ray spectrum is well fitted by an absorbed power law spectrum (Gamma=1.9 and NH = 14 x 10^22 cm-2) compatible with the AGN type II class. IGR J21178+5139 is located at RA = 21 17 47.24 Dec = +51 38 53.62 (+-10") This allows the authors to associate the INTEGRAL object with a radio/infrared source (2MASX J21174741+5138523/NVSS J211747+513855) having a 20cm flux of about 9 mJy and magnitude R~13 A faint Rosat source (1RXS J211746.9+513901) can also be seen in the Swift error box. There is no optical counterpart within the XRT error box down to the DSS-1 survey limit (R>21) implying a heavily absorbed object (R-K>8).The X-ray spectroscopy confirms the presence of intrinsic absorption (NH = 13 x 10^22 cm-2 for Gamma=1.8). More details in Landi et al. ATel 945 |
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| Mail #175 November 13 2006 |
Ibarra et al. (2006)
2006 accepted for publication in A&A report
the results of simultaneous INTEGRAL and XMM-Newton
monitoring campaigns.
The authors remark that despite large variations of the flux, the source always remains bright, which make it a very probable persistent source. The results of the spectral fittings also show variations of the absorbing column density (1.38e24 to 2.16e24 cm-2), although it always remains compton thick. Large eq width emission lines from Fe, and Ni are visible in the spectra of IGR J16318-4848. The variations of the Fe Kalpha emission line follow almost immediately the variations of the source flux (even on short time scales) whiwh suggest that the lines are produced by the illumination of small-scale optically thick matter surounding the high energy source. The authors also report evidence for a Compton shoulder in the spectra. Using the line and this shoulder they conclude that the obseuring matter is in a flattened configuration around the source, and then that we are seing IGR J16318-4848 almost edge-on. More details can be found in Ibarra et al. accepted in A&A astro-ph 0611343 Although the paper is not accepted, let me indicate you that Paizis et al. refine the position to IGR J17497-2821 with Chandra. The best X-ray position is : RA=17 49 38.037, DEC= -28 21 17.37 (90% uncertainty of 0.6") But more details can already be found in Paizis et al. 2006 submitted to ApJ atro-ph0611344 |
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| Mail #174 November 10 2006 |
Levine et al. (2006)
report the discovery of a periodicity in the ASM
light curve of IGR J18483-0311. Their analysis reveals
a 18.55+-0.03d (orbital?) period of the system
More details in Levine et al. 2006 ATel 940 Masetti et al. report some optical spectroscopy of putative counterparts to 2 new sources recently discovered IGR J00335+6126, and IGR J00254+6822. IGR J00335+6126: they identify a ROSAT source 1RXS J003357.9+612645 within the INTEGRAL error circle. In the Rosat error two relatively bright and pointlike USNO-A2.0 objects can be seen.: U1500_00600156 (R ~ 10.7) and U1500_00600240 (R ~ 13.6). Both sources are galactic stars of intermediate spectral type; According to Masetti et al. the lack of Balmer or helium emission lines in their spectra, make them unassociated to the X-ray source. IGR J00254+6822: the proposed counterpart LEDA 136991, shows a double nucleus morphology. The western nucleus has narrow [OIII], Halpha, [NII] and [SII] emission lines at redshift z = 0.012, superimposed on a reddened continuum. Line ratios are consistent with those of a Seyfert 2 nucleus. The eastern nucleus does not show any sign of activity. The authors conclude that the western part of LEDA 136991 is a possible optical candidate for the X-ray source; They further mention the positional coincidence with IRAS J00227+6805. More details in Masetti et al. 2006 ATel 941 |
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| Mail #173 November 9 2006 | Kuiper et al. (2006) report the discovery of 3 new sources with INTEGRAL-ISGRI. IGR J00254+6822 and IGR J00335+6126 were detected in a mosaic image with 4.1 Ms of exposure combining 3 years of observations of the Cassiopeia region (revolutions 142-396). The former is reported with R.A. (J2000) = 00:25:26.3 and Dec. = 68:22:49.5 (2.4' uncertainty) at an average 20-60 keV flux of ~0.8 mCrab and potential counterpart LEDA 136991(=IRAS 00227+6805), while the latter has a flux of ~0.6 mCrab, R.A. = 00:33:35.2 and Dec. = 61:26:52.2 (3.3' uncertainty) which places it ~26 arcminutes from IGR J00370+6122, and could be associated with 1RXS J003357.9+612645. The third new source, IGR J02501+5440, was detected with an average 20-60 keV flux of 1.2 mCrab in a 1.9-Ms mosaic image focused on LS I+61 303. The source is at R.A. = 02:50:11.3 and Dec. = 54:40:40.6 (3.0' uncertainty) making LEDA 2797448 a potential counterpart. More details in Kuiper et al. 2006 ATel 939 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #172 November, 8 2006 |
Combi et al. A&A 458, 761 report on some multiwavelength
observation of the Seyfert 1 IGR J18027-1455. The source is not resolved at radio frequencies, and the authors obtain a spectral index -0.75, typical of optically thin synchrotron emission originating from a jet. The NIR and Optical spectra show the presence of emission lines with a redshift z=0.0034. Furthermore the presence of a broad Halpha line further confirm the Seyfert 1 type of AGN. The authors discuss their finding and mention in particular that although the source shows typical characteristics of Seyfert 1, it is brighter than the mean at high energies. More details in Combi et al. 2006, A&A 458, 761 Masetti et al. 2006, A&A, 459, 21 continue their identification of INTEGRAL sources through optical spectroscopy. These are J05007-7047, J07565-4139, J07597-3842, J10101-5654, J12026-5349, J14175-4641, J14471-6319, J14515-5542, J14536-5522, J14552-5133, J15094-6649, J16167-4957, J16185-5928, J16207-5129, J16558-5203, J17195-4100, J17200-3116, J17488-3253, J17513-2011, J18244-5622. They started their analysis by searching for single Rosat counterparts in the IBIS error box. 18 such sources where found, which in addition showed a maximum of 3 possible Optical (V<18) counterparts. This study allowed Masetti and collaborators to possibly identify Optical counterparts of 13 INTEGRAL unidentified sources. These are J07597-3842, J10101-5654, J14175-4641, J14471-6319, J14515-5542, J14536-5522, J14552-5133, J15094-6649, J16185-5928, J16558-5203, J17200-3116, J17488-3253, J17513-2011 Further analysis allowed them to identify (or confirm) the type of those sources. 4 are Cvs (J14536-5522, J15094-6649, J16167-4957, J17195-4100) 4 are HMXBs (J05007-7047, J10101-5654, J16207-5129, J17200-3116) The remaining 12 are AGNs, half are Seyfert 1 (J07597-3842, J14552-5133, J16185-5928, J16558-5203, J17488-3253, J17513-2011), and the other half Seyfert 2. For all of them, further classification and redshift are given. More details on the strategy and the sources parameters can be found in Masetti et al. 2006, A&A, 459, 21 Patel et al. 2006 accepted in ApJ, report spectral and timing analysis of multi satellite observations of IGR J16358-4726. They first observe that any periodic outburst in this source could not occur on interval > 400 days. A joint Chandra and INTEGRAL spectrum is well fitted by an absorbed powerlaw (Gamma~0.4), with a high energy cut-off (Ecut 19 keV, Efold~12 keV) and an iron emission line, or equivalently by a comptonized spectrum. The 1.6 hour pulsation is confirmed in all data including those from ISGRI, and the authors identify a spin up of 1.9e-4 s/s. This strongly suggest a neutron star as the primary, while assuming disc accretion in the system, the author estimate a magnetic field ranging from 1e13 to 1e15 G, which may indicate IGR 16358-4726 is a magnetar. More details in Patel et al. 2006 accepted in ApJ, astro-ph 0610768 Burderi et al. 2006 accepted in ApJ, report on a timing analysis of the RXTE data of IGR J00291+5934 performed during the 2004 outburst of the source. They give a more accurate value of the spin frequency, while they estimate a the spin up rate of the source based on differnet assumptions (from 0 8.5e-13 Hz/s, to 1.17e-12 Hz/s). From the spin up values they can estimate a mass accretion rate of about 8.5e-9 solMasses/year. This result should imply a higher bolometric luminosity of the source. The authors discuss their findings and suggest that part of the accretion luminosity is not visible. All details, and alternative discussions, can be found in Burderi et al. 2006 astro-ph 0611222 Chaty et al. 2006, ATel 936 report follow up near IR observations of IGR J17497-2821. They could study their previously proposed countepart, alhtough they could not separate the different components of this object (that is blended). They remark that no variaitions of this object where found. This could be due to the fact that this is a blended object could, adn that the luminosity is of this (blended) object is dominated by a brighter component than the true counterpart itself. More details in Chaty et al. 2006 ATel 936 |
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| Mail #171 October 12 2006 | Itoh et al. 2006 ATel 914 report on the results of their Suzaku observation of IGR J17497-2821. The source is detected from 0.5 to 300 keV. The 1-60 keV spectrum is well fitted by an absorbed power law with Nh=4.6 and Gamma=1.6 A gradual cut-off is seen above 100 keV. A hint for some structures in the Fe region is seen. Some variations of flux and spectral hardness are seen along the observation. More details in Itoh et al. 2006 ATel 914 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #170 October 4 2006 |
Torres et al. 2006 ATel 909 further report on the NIR counterparts to IGR J17497-2821.
The authors present their observations of the field performed with the 6.5 m Magellan
Baade telescope in the Ks band.
They found a large number of sources in the Swift error circle.
They mention that the counterpart favoured by the 1" accurate Chandra position (Paizis et al. ATel 907),
is in fact a blend of 2 objects. The faintest of the 2 object is located at RA=17:49:38.039 Dec=-28:21:17.5 (+/- 0.1" uncertainty), and has Ks=15.9 This object is only 0.1" away from the Chandra position, and must be considered as the most likely counterpart to the high energy source. More details can be found in Torres et al. 2006 ATel 909, while a finding chart is available here, |
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| Mail #169 October 3 2006 |
Chaty et al. 2006, ATel 906 update the list of candidates
Infra red counterparts to the X-ray source.
Among 3 2 MASS sources they find 6 ohter sources in their observations.
The list of sources and their magnitudes can be found in Chaty et al. 2006 ATel 906 Paizis et al. 2006 ATel 907 report on the preliminary results of a Chandra observation of the same source. They refine the position to RA= 17 49 38.04, Dec= -28 21 17.4 with an uncertainty of about 1". This allows them to identify the source labeled candidate 1 in Chaty et al. located at RA=17 49 38.08, DEC=-28 21 17.6 as the most probable counterpart. Their preliminar analysis leads to a 1-8 keV flux of 3.1 e-10 erg/s/cm2, N_h = 4.2+/-0.1 e22 cm^-2 and Gamma = 1.15+/-0.05. More details in PAizis et al. 2006 ATel 907 Negueruela and Schurch 2006 (accepted in A&A) report searches for Optical counterparts to a certain number of INTEGRAL sources and new spectra and therefore spectral classification for some of them. IGR J11305-6256: confirmation of the system to be a low luminosity Be/XRB IGR J16207-5129: Their analysis suggests a B0 although they cannot be definite about that. The counterpart is of an earlier type than B1 in any case. This is a new Super Giant XRB J16283-4843: K counterpart. J16320-4751: confirmation that 2MASS J16320215-4752289 is the counterpart. If a OB supergiant, then it is extremely reddened J17091-3624: F8 V making the system a low mass microquasar J18406-0539: existence dubious and possible association with J18410-0535= AX J1841.0-0535 SS406 is not a promising counterpart (much) More details can be found in Negueruela & Schurch 2006 astro ph 0610006 |
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| Mail #168 September 29 2006 |
Kennea et al.
ATel 900, report analysis of
the 4 Swift observations of IGR J17497-2821.
By combining the 4 observations the authors manage to refine
the position of the source to RA(J2000)= 17h 49m 38.1s, Dec(J2000) = -28d 21m 16.9s with an uncertainty of 5.3 arcsec at 90%. This is 19" from the original position and 4" from the tentative IR counterpart from Chaty and collaborators. 2MASS 17493780-2821181 is now the only object in the Swift error circle. Their spectroscopic analysis leads to : N_H = (4.8 +/- 0.3) e22 cm-2 Gamma = 1.6 +/- 0.1 Flux = 3.3 e-10erg/s/cm2 (0.3-10.0 keV, uncorrected for absorption). Assuming a distance of 8.5 kpc for this source, and correcting for absorption, the 0.3-10.0 keV X-ray luminosity of this source is approximately 7 e36 erg/s. More details in Kennea et al. 2006 ATel 900 |
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| Mail #167 September 27 2006 |
Some news on 2 INTEGRAL sources, which happen to be: 1. the first source and < 2. the last source discovered by INTEGRAL. Kaplan et al. (published ApJ letter) report evidence of long-wavelength excesses in two highly obscured high-mass X-ray binaries (both exhibit a high column density along the line of sight of 10^23-24 cm-2): IGR J16318-4848 and GX 301-2. They performed a fit of archival near- and mid-infrared observations from 2MASS, Spitzer and MSX, with a model of emission of HMXBs (taking into account the stellar emission and a dust component blackbody emission). They then showed that the spectral energy distribution of both sources is higher in the MIR than the expected stellar emission. According to these authors, this long-wavelength excess probably suggests the presence of warm circumstellar dust at ~1000 K, which might also be responsible of the X-ray absorption. More details in Kaplan et al., ApJ, 2006, 649, L107 Chaty et al. (ATEL 897) report on infrared observations of 3 candidate counterparts of the new INTEGRAL source IGR J17497-2821. They look for counterparts near the SWIFT position RA=17:49:37.8 DEC=-28:21:18 (J2000). They report that the two 2MASS sources which are in the Swift 5" error circle (2MASS 17493780-2821181 and 2MASS 17493774-2821173) are blended in the 2MASS image. By inspecting the new JHKs images, they discover that 2MASS 17493780-2821181 itself is also a blended object, and that the object (called candidate 3) located at the East of this blended object is more reddened. They derived the galactic coordinates of candidate 3 and the IR magnitudes of the 3 candidates for 3 consecutive nights. According to them, their observations suggest that candidate 3 is the real counterpart of the source, from its infrared variability and colors, consistent with the X-ray properties. More details in Chaty et al. 2006, ATel 897 |
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| Mail #166 September 22 2006 | Laycock et al. (2006) discuss their search for the optical counterpart to IGR J17497-2821 in archival data from the Champlane survey. There are 7 candidate stars inside the Swift error circle, but all appear to be foreground objects unassociated with the galactic bulge, and none exhibit H-alpha emission. The spectral characteristics of these candidates are therefore inconsistent with the properties derived from X-ray observations. They suspect that the accompanying (likely) low-mass counterpart is difficult to identify in their data due to crowding and absorption. However, new observations taken during the current outburst could reveal the true counterpart thanks to an accompanying nova or a brightening of one of the stars in the field. Their results, and the properties of the candidate stars, are described in: ATel895. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #165 September 21 2006 | Kuulkers et al. 2006 eport further analysis of their INTEGRAL JEM-X data performed on sept 18, and present the result of a joint JEM-X+ISGRI spectrum. Their analysis shows that the spectrum is well represented by an absorbed pl with Gamma=1.93, and they give an upper limit on the absorption column density of 6e22 cm-2. They conclude that the source is in a typical hard state of X-ray binaries either with a neutron star or a black hole as primary Further to that Walter et al. 2006 report the results of a Swift ToO and other observations of the source with INTEGRAL. The source is detected up to 200 keV, and its broadband spectrum is, as reported by Kuulkers and collaborators, well represented by an absorbed power law with Gamma = 1.96+/-0.05 and a low absorption column density (NH<3.5 E22 /cm2) They also give a refined position obtained with Swift/XRT RA=17:49:37 DEC=-28:21:28 (J2000), with an error of 5 arcsec. They report the presence of two IR objects within the Swift position, and add that the source spectrum and light curve are indicative of an X-ray nova. Krimm et al. 2006 mention that the source was detected by Swift/BAT, and report that on-state detection was obtained back to Sept. 5, and was not detected after until Sept. 15. The authors mention that the source follows a general brightening and that it is of variable nature. Markwardt and Swank 2006 report the result of an RXTE observation of the field of the source. They mention that no QPO are detected but the source shows a strong red noise dominated by period longer than 1s. More details in ATel888, ATel889, ATel890, ATel891. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #164 September 19 2006 | Soldi et al. 2006 (ATel 885) report on the discovery of a new source IGR J17497-2821 during observation of the Galactic Center region. The source was discovered with ISGRI at a position RA=267.4277 Dec=-28.3443 The authors report that the source brightened from 25 mCrab (20-40) to 40 mCrab within less than 2 days. Shaw et al. 2006, further indicate that they detected the source during the Galactic Bulge monitoring performed by their team, at fluxes 45 and 50 mCrab in 20-60 and 60-150 keV repsectively. The source is also detected in JEM X. Their position is RA=267.410 Dec= -28.358 with an uncertainty of 1' at 90% level. More details can be found in Soldi et al. 2006 ATel 885 and Shaw et al. 2006 ATel 886 | Mail #163 September 15 2006 | Burenin et al. 2006 (ATel 883) report the optical identification of 2 INTEGRAL sources detected by Krivonos et al. in a paper to be published soon. IGR J01528-0326 is associated with MCG-01-05-047. The optical spectroscopy shows various lines, and the authors conclude that this object is a Seyfert 2 AGN, with a measured redshift z=0.01691 IGR J02343+3229 is associated with NGC 973, an edge on spiral Galaxy. Again the Optical spectroscopy leads to authors to conclude tha tthis source is probably a Seyfert 2 AGN, with a measured redshift z=0.01574 More details can be found in Burenin et al. 2006 ATel 883 In a paper published in ApJL, Bykov et al. 2006, report on the nature of IGR J2018+4043, usually known as IGR J20187+4041. The authors present results from multi wavelengths observations making use of INTEGRAL, Swift, the VLA and report Optical and infrared archival data. The use of Swift allows them to report a very fine position at X-ray energies (see Kennea et al. 2006 ATel 788). The joint Swift and ISGRI spectrum is well fitted by an absorbed power law with Gamma=1.3+-0.2 and Nh=6.1 e22 cm-2 An IR counterpart is found at RA=20h 18m 39.1s and Dec=+40¡ 40' 56" (+-2") with a flux of 99 mJy at 8.28micron. An extended source is found in the NIR domain, with magnitudes J=13.0, H=11.5, and Ks=10.7, while in Optical they can estimate Mred=18.1 and Mblue>22.5 At radio wevelength, the high energy source is within an extended source, but the connection between the 2 is not so clear to them. They then discuss the nature of the source, and start suggesting that it is the counterpart to the EGRET source 3EG J2020+4023. Through their analysis the authors favour a blazar as the nature of the object, although other possibilities are far from being excluded. More details can be found in Bykov et al. 2006, ApJ, 649, L21 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #162 September 6 2006 |
Masetti et al. (2006) have identified the optical counterparts of 20 IGR sources, thereby enabling the classification of
these sources into AGN (12), HMXB (4), and Intermediate Polar (IP) CV stars (4). All of the sources were observed for about
2ks each with the 1.5m CTIO telescope and spectrograph during the months of March and April, 2006. The main results of each
source are listed below.
IGR J05007-7047 The authors confirm the classification of this source as a HMXB in the LMC as was previously proposed by Sazonov et al. (2005) and Goetz et al. (2006) based on the redshift of lines in the Balmer series. The counterpart is of spectral type B2III and has a V-band optical magnitude of 14.8. IGR J07565-4139 The optical spectrum is compatible with a Sey-2 galaxy (although blended with a foreground star) at a redshift of z=0.021(1). IGR J07597-3842 Coordinates (J2000) for the optical companion are R.A. = 07:59:41.819, Dec. = -38:43:56.03 (error <0.1"), and the source is classified as a Sey-1.2 at z=0.040. The central black hole (BH) mass is estimated at 2x108 Msol. IGR J10101-5654 Its optical coordinates are R.A. = 10:10:11.866 and Dec. = -56:55:32.06, and the spectral type is an intermediate to early-type giant which classifies the source as a HMXB. The spectrum indicates heavy absorption by dust along the line of sight. Another bright object that is just within the Swift error circle is shown to be a normal mid-type star and hence not the true counterpart. IGR J12026-5349 This source is a Compton-thick Sey-2 galaxy located at z=0.028. IGR J14175-4641 The optical position of the proposed counterpart is R.A. = 14:17:03.662 and Dec. = -46:41:41.19. This source is probably a Sey-2 galaxy at a redshift of z=0.076, but the lack of a sub-arcsecond soft X-ray position means the association is still tentative even if it is the most likely one. IGR J14471-6319 At R.A. = 14:47:14.881 and Dec. = -63:17:19.24, with a redshift of z=0.038, IGR J14471-6319 is a Sey-2 galaxy. IGR J14515-5542 This Sey-2 galaxy at z=0.018 has R.A. = 14:51:33.131 and Dec. = -55:40:38.40. IGR J14536-5522 Already identified as a CV (e.g. ATel:783), this source has R.A. = 14:53:41.055 and Dec. = -55:21:38.74, and is located ~190 pc away. Its strong magnetic field suggests a Polar CV rather than an IP CV classification. IGR J14552-5133 With an accuracy of around 1" (i.e. less than for the others), the coordinates of the optical counterpart are R.A. = 14:55:17.8 and Dec. = -51:34:17. The source is likely to be a narrow-line (NL) Sey-1 galaxy at z=0.016 with a central BH mass of 2x106 Msol, but a sub-arcsecond X-ray position could help confirm this association. IGR J15094-6649 At R.A. = 15:09:26.013 and Dec. = -66:49:23.29, this CV star (c.f. ATel:783) is ~140 pc away. Although the error circle of the ROSAT counterpart contains 2 bright sources, the refined position from this optical campaign and the accompanying spectra are enough to exclude one of them. IGR J16167-4957 Identified as a CV in ATel:786, this source has a new distance estimate of ~170 pc. IGR J16185-5928 The position of the optical counterpart is R.A. = 16:18:36.441 and Dec. = -59:27:17.36. This source is a NL Sey-1 galaxy at z=0.035 with a central BH mass of 2.8x107 Msol. IGR J16207-5129 This source was already classified as a HMXB (c.f. ATel:783). The optical spectrum presents heavy reddening from dust along the line of sight, and indicates a companion that is an early-type supergiant situated at ~4.6 kpc. IGR J16558-5203 With R.A. = 16:56:05.618 and Dec. = -52:03:40.87, this Sey 1.2 galaxy at z=0.054 has a central BH mass of 7.8x107 Msol. IGR J17195-4100 A new distance estimate of ~110 pc is proposed for this source which was already classified as a CV in ATel:783. IGR J17200-3116 The optical coordinates of this source are R.A. = 17:20:05.913 and Dec. = -31:16:59.65. Its spectral shape is reminiscent of other companions of HMXBs and it also features heavy absorption by dust, but no other information about the spectral type or distance could be gleaned from the observations. IGR J17488-3253 The spectrum is compatible with a Sey-1 AGN at z=0.020. The coordinates of the optical counterpart are R.A. = 17:48:55.129 and Dec. = -32:54:52.15. IGR J17513-2011 A position of R.A. = 17:51:13.623 and Dec. = -20:12:14.58 is determined for the optical counterpart to this Sey-1.9 galaxy at z=0.047 and with a central BH mass of 106 Msol. IGR J18244-5622 This is a Sey-2 galaxy in the Compton-thin regime situated at z=0.017. Their results are described in Masetti et al. (2006) accepted in A&A: astro-ph 0608394 In addition, Burenin et al. (2006) report on the optical identifications of 4 IGR sources detected in an upcoming article by Krivonos et al. (2006). IGR J03334+3718 is associated with a Sey-1 AGN at z=0.05471 and coordinates R.A. = 03:33:18.8 and Dec. = +37:18:11. Another Sey-1 AGN, IGR J13038+5348, is associated with MCG+09-21-096 and is at z=0.02988. Chandra observations of IGR J18048-1455 lead to a refined X-ray position of R.A. = 18:04:38.96 and Dec. = -14:56:47.3, and a spectrum compatible with that of a galactic HMXB. IGR J20006+3210 is also classified as a galactic HMXB given the spectral shape of the optical counterpart at R.A. = 20:00:21.9 and Dec. = +32:11:23. Their results are described in Burenin et al. 2006: ATel:880 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #161August 14 2006 | Another new source has been discovered by Kuulkers et al. (2006) thanks to the Galactic Bulge Monitoring Program. Dubbed IGR J17354-3255, it has the coordinates R.A. (J2000) = 17:35.4 and Dec. = -32:55 with an error radius of 4'. The source was detected in 2 consecutive pointings of ~1.8 ks each on April 21, 2006, between 04:27 and 05:29 a.m. (UTC). The average flux in the 20-60 keV range is 18 mCrab. JEM-X was not operating at the time, and there are no other known high-energy sources inside the error box. Their results are described in Kuulkers et al. 2006: ATel:874 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #160August 9 2006 |
Sguera et al. (2006) report the discovery of 3 new IGR sources in the 17-30 keV energy range with ISGRI.
All 3 sources exhibit behavior reminiscent of other SFXTs. Each appears with a significance above 7 sigma in a single
pointing lasting ~2 ks without detections in previous or subsequent pointings. The relevant parameters of the sources are listed below:
IGR J18159-3353 R.A. (J2000) = 18h15.9m, Dec.=-33d53', uncertainty=4' Average Flux (17-30 keV) = 31(+/-4) mCrab IGR J20188+3647 R.A. = 20h18.8m, Dec.=+36d48', uncertainty= 3.4' Average Flux = 33(+/-5) mCrab IGR J21117+3427 R.A. = 21h11.8m, Dec.=+34d28', uncertainty= 3.5' Average Flux = 75(+/-9) mCrab Only one of these objects has a known X-ray source in its error circle: EXMS B2016+366 is about 2.8' away from the ISGRI position for IGR J20188+3647 and could be the X-ray counterpart. Their results are described in Sguera et al. 2006: ATel:873 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #159July 26 2006 | Hinton & Aharonian (2006) discredit the possible relationship between IGR J1745.6-2901 and the TeV source HESS J1745-290. They believe that synchrotron and inverse Compton emission from a diffuse 20 pc source is a viable yet unlikely scenario given that electrons would lose energy too quickly. This cooling-loss problem was previously raised by Neronov et al. (2005, astro-ph/0506437). Their results are described in an article submitted to ApJ available at astro-ph 0607557. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #158July 25 2006 | Paizis et al. 2006 ATel 865 report the discovery of 3 new sources in a systematic analysis of INTEGRAL archival data. Each of the 3 sources was visible in only one pointing (in 2004). These are IGR J10043-8702 RA= 10h 04m 18s Dec= -87¡ 02' 07" (+-3.4') with a 17-40 keV flux of 22 mCrab IGR J10500-6410 RA= 10h 50m 05s Dec= -64¡ 10' 10" (+-4') with a 17-40 keV flux of 32 mCrab IGR J15283-4443 RA= 15h 28m 24 Dec= -44¡ 43' 51" (+-3.0') with a 17-40 keV flux of 65 mCrab Some more details are available in Paizis et al. 2006 ATel 865 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #157July 21 2006 | Barlow et al. 2006 (accepted in MNRAS) report on properties of CVs observed with INTEGRAL/IBIS. They mention the discovery of a new INTEGRAL source IGR J06253+7334, which they associate with the Rosat source 1 RXS J062518.2+733433, an Intermediate Polar. The best IBIS position is RA=06h 25m 16s Dec=73o 34' 37" Barlow and collaborators through a study of correlations between the Downes & Shara catalogue and the most recent mosaic produced by the INTEGRAL survey team, confirm the identifications of IGR J00234+6141, J15479-4529, J17303-6016, and J21335-5105 as a CV for the first, and IPs for the last 3. They then study the properties of the CVs detected by INTEGRAL and add to their sample 4 more IGRs recently identified as candidate CVs. For each of the sources, they report, when known, the orbital period, the spin period the distance, the type and the X-ray counterpart. They also present the results of the spectral analysis of the IBIS data for each source. They discuss the results of their analysis, and mention in particular that most of the detected CVs are magnetic systems (mostly IPs). The spectral charateristics of those sources in the 20-100 keV band are quite similar, and compatible with previous analysis, the spectra can be well fitted by a power law or a thermal bremsstrahlung. More details on these sources (and all CVs detected by INTEGRAL) can be found in Barlow et al. 2006 (MNRAS accepted) astro-ph 0607473 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #156June 21 2006 | Molina et al. (accepted (?)in MNRAS) report on INTEGRAL observations AGNs seen through the Galactic plane, two of which having been discovered by INTEGRAL, namely IGR J18027-1455 & J21247+5058. Since these two objects have been discovered only recently, the authors could only analyse data from INTEGRAL/ISGRI. The source's spectra is well represented by a power law in both case with photon indices 2.13 and 1.87 for J18027-1455 and J21247+5058 respectively. The authors also studied the possible presence of a high energy cut-off in the spectra of both sources , but they don't obtain strong constraints on it with lower limits of 40 and 30 keV for the former and the latter respectively. The authors discuss their findings (including all sources together) in a context of high energy emission of AGNs and report in particular that they don't observe any particular correlation between the photon index and the cut-off energy as has been claimed by others More details can be found in Molina et al. 2006 MNRAS (accepted?) astro-ph0606488 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #156June 12 2006 | Walter et al. describe the imaging, timing and spectral properties of 10 IGR sources from combined XMM-Newton and ISGRI observations. All positions are reported in J2000 coordinates with an error radius of 4 arcsec. The Xspec spectral model used to fit the combined XMM and ISGRI data is an absorbed (in units of 1022 atoms/cm2) compTT with a gaussian for an iron line and a blackbody component for the soft excess. The most relevant properties of sources for which this information is not cited elsewhere are listed below: IGR J16418-4532: The refined position of R.A. = 16:41:51.0 and Dec. = -45:32:25, places it 2.4 arcsec from the possible IR counterpart 2MASS J16415078-4532253 with a K-band magnitude of 11.5. A pulsation of ~1200 s is present in the XMM data with a pulse fraction of ~60%. The source spectrum presents little soft excess and a marginal K-alpha line (EW < 34 eV), but it is strongly absorbed (nH = 10.0+-1.2). The unabsorbed broadband flux (2-100 keV) is 1.3x10-10 ergs/cm2/s. Its likely classification is a persistent HMXB pulsar. IGR J16479-4514: Its X-ray position is R.A. = 16:48:06.6 and Dec. = -45:12:08 which is only 1.3 arcsec away from 2MASS J16480656-4512068 (K-band magnitude of 9.8). The source is a persistent HMXB which demonstrates strong variability on short timescales, but we were unable to search for pulsations in the XMM data as the low source count rate meant that the light curve was dominated by the background. The spectrum is best fit with a column density of 7.7+-1.7. The upper limit on the iron line's EW is 280 eV, and the unabsorbed flux is 1.8x10-10 ergs/cm2/s. IGR J16465-4507: The XMM-Newton position (R.A. = 16:46:35.5 and Dec. = -45:07:04) of this transient HMXB is 2.6 arcsec from 2MASS J16463526-4507045 (K-band magnitude of 9.8). A pulse period of 227+-5 s is discovered in the XMM data with a pulse fraction of ~80%. The same pulsation was not found during ISGRI observations of the source in a relatively bright state. The source spectrum is strongly absorbed (nH = 60+-10) with an upper limit on the EW of the iron line at 60 eV. The soft excess is large and can not be accounted for by a partial-covering absorber. The unabsorbed flux is 2.8x10-10 ergs/cm2/s. The source type is a transient HMXB with a B supergiant companion. IGR J17597-2201: The best position for the source is R.A. = 17:59:45.7 and Dec. = -22:01:39 which is 4.9 arcsec from 2MASS J7594556-2201435 (K-band magnitude = 12.9). The spectrum presents an absorption of 4.5+-0.7, and the unabsorbed flux is 3.4x10-10 ergs/cm2/s. The soft-excess component can be explained by a partial-covering absorber. In this case, the nH is 2.70+-0.15. No pulsations could be found in the XMM data which was affected by a large background. The source is a persistent HMXB with a late-type companion. IGR J18027-2016: At R.A. = 18:02:42.0 and Dec. = -20:17:18, the source is only 1.1 arcsec from 2MASS J18024194-2017172 (K-band magnitude = 11.4). The absorption is 9.1+-0.5, the iron line EW is ~33 eV, and the unabsorbed flux is 1.1x10-10 ergs/cm2/s. The pulsation of ~139 s and the orbital period of 4.57 d were already reported by Hill et al. (2005), which classifies this source as a persistent HMXB pulsar with an OB supergiant companion. Details of these and other sources are provided in Walter et al. (2006, A&A Vol. 453, pp 133-143) : A&A Vol. 435, p. 133 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #155May 29 2006 | Thompson et al. 2006 describe the orbital parameters of the heavily-obscured X-ray pulsar IGR J16393-4643 as observed by RXTE. The most likely solution for the orbital period is 3.6875(6) days (with a semi-major axis of 43+/-2 light-s). This places the ~900s pulsar in the region of wind-fed accretors in the Corbet diagram, and suggests a companion mass of 6.5+/-1.1 Mo (or up to 14 Mo if eccentricity is included). These observations support the supergiant HMXB classification. The authors determine a pulse period of 911.3(1)s which could imply that the accretion rate has increased since the time of the XMM-Newton and ISGRI observations. More information can be found in Thompson et al. 2006, accepted in ApJ astro-ph 0605657 A new IGR source dubbed IGR J17364-2711 was discovered by Chelovekov et al. 2006. This source was found while searching for short (~5-500s) bursts in INTEGRAL lightcurves from the first 1.5 years in orbit. The source had a peak flux in ISGRI (15-25 keV) of 1.6(3) Crab at (UTC) 14:41:30 on 17-02-2004. The burst lasted 13 seconds and was outside the JEM-X FOV. The ISGRI source spectrum is very soft with bins above ~30 keV representing upper limits. IGR J17364-2711 was not detected in a mosaic image combining observations before and after the burst, but excluding the pointing in which the burst took place. The 3-sigma limit on persistent 15-25 keV emission is 4 mCrab. The source position (J2000) is R.A. = 17:36:28 and Dec. = -27:11.9 (2' error) which is about 15' away from 1RXS J173602.0-272541. Please see Chelovekov et al. 2006 Astron. Lett. 32, 456 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #154May 24 2006 |
Barba, Gamen and Morrell
report on some results of
their spectroscopic monitoring of the HD 74194.
After recalling that the star is a 08.5 Ib (Walborn 1973), the authors
discuss their findings, and mention in particular the change of the Halpha profile from a double-peaked
emission, to a P Cyg-like profile. They also detected radial velocity variations in the HeI
and HeII absorption lines with an amplitude of about 35 km/s.
They then compare the spectrum of the source to that published by Pelliza et
al (2006) on another SFXT IGR J17544-2619, which leads them to further suggest
that HD 74194 is th genuine counterpart to IGR J08408-4503, and that theis source
is the same kind of SFXT than IGR J17544-2619
More details in Barba et al. 2006
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| Mail #153May 23 2006 |
Kennea & Campana
report the results of a Swift XRT snapshot observation of
the newly discovered supergian Fast XRT candidate IGR J08408-4503.
Although the source is very dim, they refine the X-ray position to
RA = 08h 40' 47.97",
Dec = -45deg 03' 29.8"
+-5.4 " @90%.
The position is at less than 2" from he suggested optical counterpart HD 74194 (LM Vel)
which further suggest both sources are associated.
The 0.5-10 keV flux of the source was 1.9e-13 erg/cm2/s at the tie of the Wift bservation, which
leads to a luminosity of 2e32 erg/s assuming a distance of 3 kpc (best estimate of the distance
to LM Vel)
The authors further discuss the possible origin of the X-ray emission at the time of their observation
and favour it to be the quiescent emission from IGR J08408-4503.
More details can be found in Kennea & Campana 2006
Pelliza, Chaty and Neguerela (2006 accepted in A&A) report the results of their IR/Optical observations of the field of IGR J17544-2619. Although 5 candidates can be found in the XMM error circle, the Chandra position exclude all the candidate but the brightest. Hence the authors further conclude that this is the true counterpart to the X-ray source. They performed spectroscopic analysis of this source in order to establish its spectral type. They find He II lines int he spectrum, and from the ratio of He II to He I they identifythe source as a O 9, with an estimated mass of 25-28 solar masses. They report the magnitudes of the source in several bands, and by comparison with ealier publish results show that all are consistent but the J and H magnitudes that seem to have evolved. Pelliza et al. suggest that this may be related to the X-ray activity of the source. The magnitudes measurments lead them to further conclude that the star is a O 9Ib at a distance of 2.1-4.2 kpc in the Scutum-Crux arm of our Galaxy. The author discuss all their results and suggest in particular (by the lack of radio detection) that the compact object is a neutron star. More details can be found in Pelliza, Chaty and Neguerela 2006 accepted in A&A astro-ph 0605559 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #152May 22 2006 | Brandt et al. (2006) report a refined position of the new INTEGRAL source IGR J08408-4503, obtained with JEM X during the outburst that led to the detection of the source. Their refined position is RA = 08h 40m 48.7s, Dec = -45o 03' 41'' (J2000, +-46'' at 90% confidence). The supergiant star HD 74194 proposed as the counterpart to the sourc is still contained in this smaller error box, which strenghtens the possible assocition between the 2 sources. The authors add, however, that inspection of the IR and Optical data from 2MASS and DSS show that this source is not unique in the refined error box of the IGR sources. A finding chart is available at here while more details in Brandt et al. 2006 ATel 817 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #151May 22 2006 | Masetti et al. (2006) report the analysis of archival optical spectra of HD 74194, the putative Optical counterpart to the Supergiant FSXT candidate IGR J08408-4503. They identify in these spectra Halpha emission line and 2 HeI absorption lines. By analogy with other systems, they conclude that this is the true counterpart to IGR J08408-4503,, and that the X-ray source is indeed a Supergiant Fast XRT. Looking at the field of IGR J15539-6142, the authors find a emission line early type star in the error box of the x-ray source, which they prefer as the counterpart to IGR J15539-6142. The star is HD 141689 which is classified a a B2/B3 star. More details can be found in Masetti et al. 2006 ATel 815 Markwardt & Krimm report renewed activity of another Fast X-ray transient IGR J16479-4514, detected with the BAT telescope onboard Swift. Few more details in Markwardt & Krimm 2006 ATel 816 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #150May 19 2006 | Mereghetti et al. (2006) report that archival analysis of this region revealed that this source underwent an outburst lasting 2 hours during July, 2003. At its peak, the source flux (20-60 keV) reached 6x10-10 erg/cm2/s. The position from this detection is R.A. (J2000) =08:40:46 and Dec.=-45:04.2 (uncertainty of 2.6 arcminutes) which is consistent with the position given upon its discovery, and consistent with the position of the supergiant HD 74194. Thus, the source is likely to be a new member of the class of SFXTs. More details in Mereghetti et al. 2006 ATel 814 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #149May 18 2006 | Gotz et al. (2006) report the observation of the outburst from a new source IGR J08408-4503 during INTEGRAL deep exposure of the Vela region. The source is detected by IBIS and JEM X during a short (900s) X-ray outburst at a best position RA = 08h 40m 50s, Dec = -45deg 03' 07'' (J2000, +/-2.5 arcmin @90% error) with a 20-40 keV peak flux of 250 mCrab A preliminary joint JEM-X/ISGRI fit of the peak spectrum, integrated over 300 s, using a black body model, yields a temperature of 4.51 keV and a 4-50 keV flux of about 2e-9 erg/cm2/s. Gotz et al. report de presence of a 7th mag O star located at a distance of 1.7 kpc (HD 74194, a supergiant member of the Vela OB1 association) in the INTEGRAL error box. If the star and the X-ray object are associated, then the peak luminosity of IGR J08408-4503 is about 1e36 erg/s, which rules out a coronal flare as the origin of the X-ray outburst. The authors briefly discuss the type of the source and mention that it is likely a new member of the supergiant fast x-ray transient, although a peculiar GRB cannot completely be ruled out. More details in Gotz et al. 2006 ATel 813 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #147May 16 2006 | Keek et al. (2006) report the discovery of 5 new sources from their analysis of an ultra deep mosaic of the the Circinus region. All sources have a significance greater than 6. These are : IGR J14003-6326 has a 20-60 keV flux of 0.97 mCrab, and is potentialy the hard X-ray counterpart to 1RXS J140041.2-632623: RA= 14 00 20.3 dec= -63 26 9 +- 3.6' IGR J14298-6715 has a 20-60 keV flux of 0.98 mCrab, and is potentialy the hard X-ray counterpart to 1RXS J142959.9-671447 RA= 14 29 49.8 Dec= -67 15 24 +- 3.7' IGR J14331-6112 has a 20-60 keV flux of 0.82 mCrab RA=14 33 6.2 Dec=-61 12 23 +-3.9' IGR J14471-6414 has a 20-60 keV flux of 0.68 mCrab and is potentialy the hard X-ray counterpart to 1RXS J144628.3-641627 although the Rosat source lies outside the 90% error circle of INTEGRAL RA=14 47 5.5 Dec=-64 14 37 +- 4.1' IGR J15539-6142 has a 20-60 keV flux of 1.37mCrab and is spatially coincident with ESO 136-6 a Type S Galaxy: RA =15 53 53.9 Dec=-61 42 0 +- 4.0' More details in Keek et al. 2006 ATel 810 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #147May 8 2006 | Tovmassian et al. (2006) report on their analysis of optical spectroscopy of a candidate counterpart to IGR J16195-4945. The spectrum of this object shows absorption lines but none of the emission lines that are expected from an X-ray binary system, and is consistent with that of a late F-type star. Its source reddening is too low to be compatible with the large extinction that was recently reported by Tomsick et al. (2006, c.f. Mail #146). Taken together, these facts demonstrate that this object is a foreground dwarf star and not the giant star that is expected to be the likely counterpart. More details in Tovmassian et al. 2006 ATel 804 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #146May 8 2006 |
Tomsick et al. (2006) describe their analysis of Chandra observations of 4 IGR sources, complemented with IR/optical data. All 4 targets present
a soft X-ray counterpart in the INTEGRAL error circle, as well as optical counterparts within the Chandra error circle. A few of of the X-ray and optical parameters
for each source are listed below:
IGR J16167-4957: The Chandra position is R.A. (J2000) = 16:16:37.74 and Dec. = -49:58:44.5 (0.6" error radius for all sources) which confirms the association with 1RXS J161637.2-495847. An absorbed power-law fit to the Chandra spectrum yields a column density of ~0.5x1022 at/cm2 (lower than the absorption expected along the line of sight) with a spectral index of ~1.1. Inclusion of the ISGRI spectrum reveals a possible high-energy cutoff. The position from Chandra lies on a source with a J-band magnitude of 14.86(6) which could be a blend of 3 sources or more. The spectral type indicates that the companion is later than A0V which rules out a HMXB. With a distance estimated at 1.8-4.2 kpc, its 0.3-10 keV luminosity is ~4.7x1034 ergs/s (for d=3kpc). IGR J16195-4945: Its refined position of R.A. = 16:19:32.20 and Dec. = -49:44:30.7 is 1.2' away from HD 146628 which rules out an association with this particular supergiant. When an absorbed power-law is fit to the Chandra spectrum, the absorption is ~7x1022 at/cm2 (larger than the galactic absorption) and Gamma ~ 0.5, making it the only one of the 4 sources that might be a member of the class of heavily-absorbed objects. An infrared counterpart (possibly from 2 blended sources) with a J-band magnitude of 13.57(3) is located at the Chandra position. The distance to the companion is hard to constrain (between 3-15 kpc) which hinders the ability to identify its spectral type, but the companion is expected to be an O, B or A supergiant star, and thus the system is a HMXB. Assuming a distance of 5 kpc, its 0.3-10 keV luminosity is ~1.4x1034 ergs/s. IGR J16207-5129: At a position of R.A. = 16:20:46.26 and Dec. -51:30:06.0, this source can no longer be associated with HD 146803. The spectral index from an absorbed power-law fit to the Chandra data is ~0.5 while its column density of ~3.7x1022 at/cm2 is marginally higher than the galactic absorption. Of the 4 sources, the 0.3-10 keV lightcurve of this source shows the most variability, and its broadband spectrum presents the best case for a high-energy cutoff. The infrared counterpart associated with this source has a J-band magnitude of 10.44(2), and a stellar temperature > 18,000 K which indicates that the system is a HMXB. The distance to the source is estimated to be between 3 and 10 kpc which, if assuming d=5 kpc, gives a 0.3-10 keV luminosity of ~1.3x1035 ergs/s. IGR J17195-4100: The refined position of this source is R.A. = 17:19:35.58 and Dec. = -41:00:53.6 which is 0.7" away from USNO-B1.0 0489-0511283, and therefore (along with supplemental IR/optical analysis) the USNO source must be considered as the optical counterpart. The Chandra lightcurve shows some variability. However, the absorption derived from the model (an absorbed power-law with Gamma~1.1 and nH~8x1020) is significantly lower than the galactic absorption. Thus, the source must be near and when the upper limit on the extinction is considered, the derived upper limit to the magnitude implies the source type of the companion can not be a supergiant or OB main sequence star, but must be later than A3. At a maximal distance of 2.6 kpc, the 0.3-10 keV luminosity is <2.0x1034 ergs/s. Their results are described in Tomsick et al. (2006) accepted for ApJ, available through astro-ph: astro-ph/0603810 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #145April 28 2006 | Rodriguez et al. 2006 report on the preliminary results of simultaneous observations of IGR J19140+0951 with INTEGRAL, Swift and RXTE. The source was in the faintest state ever observed (detected). It is not detected by INTEGRAL/ISGRI with a 20-40 keV 3-sigma upper limit of 4.5 mCrab. A simple absorbed powerlaw gives a reasonable representation of the Swift/XRT and RXTE/PCA spectrum between 1 and 18 keV. The value of the absorption is 9.1 -3.0 +3.5 cm-2 (at 90%), the power law photon index Gamma=1.7 +-0.3. The 1-20 flux is 1.54 e-11 erg/s/cm-2 (Swift normalization), and the 1-20 keV unabsorbed flux is 2.47 e-11 erg/s/cm2. We mention that this flux is about 5 times fainter than the dimmest observation published so far, and about 150 times fainter than the brightest state of the source we observed with INTEGRAL. This gives a rough estimate on the lower limit of the amplitude of the flux variations this source can undergo. We add that the general behaviour of the source (its large absorption column density, the large amplitude of the variations of the X-ray flux) suggests that IGR J19140+0951 is truly another member of the class of heavily absorbed source unveiled by INTEGRAL. More details in Rodriguez et al. 2006 ATel 800 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #144April 26 2006 | in a paper accepted in A&A, Masetti et al. 2006 report on their optical observations of the field of 6 IGRs. IGR J00234+6141: They confirm this source is a CV, probably an Intermediate Polar, that they caught in quiescence. Their analysis leads to an estimate of its distance of about 300 pc IGR J 01583+6713: They confirm that this is a transient Be HMXB which they can locate at 6.4 kpc from the Earth. IGR J 03532-6829: Masetti and collaborators associate this source with PKS 0352-686 and determine it to be a BL Lac object at z = 0.087. Interestingly in their search for counterparts, these authors report the positional association of the already proposed Rosat source (J035257.7-683120), and the radio object SUMSS J035257-683118. X-ray emission from this position had already been detected by Einstein and RXTE. The optical magnitude of the PKS object are the following B~13.6 and R~12.5 IGR J06074+2205: this is as already suggested a likely Be HMXB that the authors locate at ~1kpc from the Earth, however this should be taken with caution. IGR J13091+1137: probably a XBONG likely hiding an absorbed AGN at z=0.025. Note that the authors further report that the total optical magnitude of NGC 4992 (the position of which is consistent with the Chandra counterpart to the IGR source) is B~14.5, while its nucleus is also a radio source FIRST J130905.5+1138803 with a flux density at 1.4 GHz of 2.01 mJy. IGR J20286+2544: as for the previous source, the bibliographical search on this object led the authors to report that a single 27.4 mJy radio source is present in the INTEGRAL error box, coincident with an B~15.4 and z=0.142 galaxy MCG +04-48-002, although just outside the INTEGRAL error box another bright radio source is seen also coincident with a bright optical Galaxy NGC 6921. The Optical observations of Masetti et al. prove that MCG +04-48-002 is the counterpart to the IGR source, although as they mention, a contribution from NGC 6921 to the hard X-ray emission cannot be excluded. From a fine analysis of their observations, these authors concude that IGR J20286+2544 is a starburst/H II galaxy at z=0.013, hiding a Seyfert 2 nucleus in the compton thick regime More details can be found in Masetti et al. 2006 accepted in A&A, astro-ph 0604482 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #143April 18 2006 | Thompson et al. report on the orbital parameters of the X-ray pulsar IGR J16393-4643. These authors have carried out a pulse timing analysis of data from RXTE to determine the orbital parameters of the source. The most likely orbital orbital period is 3.688+/-0.001 days, although two other solutions (8.1 and 50.2 days) cannot be completely ruled out. Thompson et al. report a mass function of 6.5+/-1.1 solar masses which confirms that IGR J16393-4643 is a high-mass X-ray binary system. The 3.7 day orbital period and the previously known ~910 s pulse period place the system in the region of the Corbet diagram populated by supergiant wind accretors More details can be found in Thompson et al. (2006, ATel 786). Kennea et al. report the detection of IGR J20187+4041 with Swift. Using the XRT onboard they refine the position to R.A. (J2000) = 20:18:38.5, Dec. = +40:41:00.4 (+/- 4.2 arcsec at 90%), which is consistent with both the INTEGRAL source and the EGRET source 3EG J2020+4017. Their spectral analysis with a simple model of an absorbed power law leads to Gamma = 0.7(+2.2,-0.2) and nH = 4(+6/-3)e22 cm^{-2}. Kennea et al. also report the identification of a possible NIR counterpart of the source in the 2MASS catalog centered at R.A. = 20:18:38.73, Dec. = +40:41:00.1 (2.6 arcsec from the XRT position), with magnitudes J=14.9, H=12.7, Ks=12.1. The authors discuss their findings and suggest the source could either be a Galactic XRB or an AGN. More details in Kennea et al. (2006, ATel 788). Tuerler et al. report on the discovery of two new faint hard X-ray sources in the GC. IGR J17536-2339 has a flux of 11.0 mCrab between 20 and 60 keV and is located at R.A. = 17:53:38, Dec. = -23:39.2. IGR J17541-2252 has a 20-60 keV flux of 9.8 mCrab and lies at R.A. = 17:54:04, Dec. = -22:52.3 (+/-4' for both sources). The authors mention that SAX J1753.5-2349 is situated approximately 10 arcmin from IGR J17536-2339, and they cannot completely rule out the association between the 2 sources. The RXTE scanning of the GC showed no sources at these positions, which could indicate that they are supergiant fast X-ray transients or highly absorbed. More details can be found in Tuerler et al. (2006, ATel 790). Galloway has derived an upper limit of 6 kpc on the distance to the accreting millisecond pulsar IGR J00291+5934 based on its predicted burst rate and duty cycle from RXTE observations. More information can be found in Galloway (2006, astro-ph/0604345). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #142March 31 2006 | Masetti et al. report on the results of Optical observations of the field of 6 IGRs. After briefly presenting their method for the optical identification, these authors report the following: IGR J05007-7047 (a.k.a. IGR J05009-7044 from Gotz et al. 2006): detection of Halpha emission, balmer lines in absorption. Redshift onsistent with that of the LMC. Likely HMXB in LMC. IGR J14536-5522: USNO-A2.0 source U0300_22436308 brightest object in XRT and Rosat error boxes. RA = 14 53 41.16, Dec = -55 21 37.4 Spectrum classify it as a CV. IGR J15094-6649: USNO source U0225_21896607 RA = 15 09 26.00, Dec = -66 49 23.4 Spectrum classify it as a CV IGR J16167-4957: Balmer, HeI and HeII emissions at z = 0. U0375_26829054 at RA = 16 16 37.78, Dec = -49 58 44.7 -> spectrum is typical of a CV. IGR J16207-5129: U0375_27093111 RA = 16 20 46.28, Dec = -51 30 06.3 Halpha emission at redshift 0 superimposed on a reddened continuum. source is likely a HMXB. IGR J17195-4100: U0450_27095307 RA = 17 19 35.91, Dec = -41 00 53.7, Balmer and He emissions at z = 0 similarly to CVs. More details in Masetti et al. 2006 Atel 783 Note that the 3 latters are deeply analysed (Chandra, IR/Optical) in a paper by Tomsick and collaborators, submitted to ApJ some time ago. We will report deeply on this paper when it is accepted. It is, however, available on astro-ph Tosmick et al. 2006, ApJ Submitted astro-ph 0603810 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #141March 30 2006 | Brandt and his collaborators report the discovery of a Type I X-ray burst in IGR J17254-3257 in archival JEM-X data. The burst occured on Feb 17, 2004, had a rise time <5s and efolding decay time of 15 sec.the peak flux is 0.8 Crab in the 3-30 keV JEM-X range. more Details in Brandt et al. 2006, Atel 778 Corbet et al. 2006, analysing the Swift/BAT light curve of IGR J16418-4532 taken since 2004 dec 21 and 2005 Sep 17 have found a modulation at ~3.75 days. This is confirmed by the RXTE/ASM light curve. The authors give estimate of the ephemeris while comparing the data obtained with the two instruments. More importantly they report the possible presence of a total eclipse in the light curve from BAT. The authors further suggest the system contains a supergiant primary. More details can be found in Corbet et al. 2006 Atel 779 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #140March 29 2006 | Sguera et al. (2006, astro-ph/0603756) describe the characteristics of 7 IGR sources that are supergiant fast X-ray transients (SFXT) or SFXT candidates. Three sources have optical counterparts that were previously confirmed as supergiants: IGR J11215-5952, IGR J17544-2619 and IGR J18410-0535. They present peak fluxes of ~40 mCrab (20-40 keV), ~240 mCrab (20-60 keV) and ~120 mCrab (20-80 keV), respectively. Because their behavior is similar to other SFXTs, four other sources have probable supergiant optical counterparts: IGR J16195-4945, IGR J16418-4532, IGR J16479-4514 and IGR J17407-2808. Their peak fluxes are ~17-35 mCrab (20-40 keV), ~80 mCrab (20-30 keV), ~120 mCrab (20-60 keV) and ~805 mCrab (20-60 keV), respectively. The duration of the outbursts ranged from around 3 minutes for IGR J17407-2808 to around 10 hours (IGR J17544-2619), with most outbursts typically lasting a few hours. IGR J17391-3021 (=XTE J1739-302): This source has a peak flux of up to ~480 mCrab in the 20-60 keV range with outbursts that last a half-hour to 14 hours. Their results are described in Sguera et al. (2006) which is accepted for publication in ApJ: astro-ph/0603756 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #139March 28 2006 | Bikmaev et al. (2006, astro-ph/0603715) have identified the optical counterpart to IGR J00234+6141. Using optical observations with the 1.5-m Russian-Turkish Telescope combined with X-ray data from Swift, the authors determined that the counterpart is a CV star based on its strong emission lines and zero redshift. An independent observation of the field by Halpern & Mirabel (2006) also led them to the conclusion that the CV should be associated with IGR J00234+6141. The coordinates of the CV are R.A. (J2000) 00:22:57.6 and Dec. = +61:41:08. Furthermore, the optical lightcurve shows a modulation of 570 s which corresponds to the spin period of the white dwarf. Therefore, the source is classified as an intermediate polar, weakly-magnetized white dwarf. Their results are described in Bikmaev et al. (2006) accepted for publication in Astronomy Letters: astro-ph/0603715 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #138March 27 2006 | Smith et al. (2006, ATel 773) report that as predicted the outburst of IGR J11215-5952 has apparently ended. From the analysis of the RXTE follow ups of the source the authors give lower and upper limits to the total duration of the outburst of 2.0 and 3.4 days. They also report the discovery of a possible pulsation at 195 s. Bassed on all findings recently reported, Smtih et al. discuss the possible type of the system and further suggest that it is more compatible with a superfast X-ray transient rather than a Be/neutron star system. The authors also report some spectral results, and mention in particular the relative constancy of the spectra alog the outburst. The outburst light curve is available here while more details are given in Smith et al. 2006 ATel 773 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #137March 22 2006 | Following the recent outburst of the superfast X-ray transient IGR J11215-5952 that was announced in ATel:766, Steeghs et al. (2006, ATel:768) report that they observed the source with the Swift XRT and obtained a refined position of R.A. (J2000) = 11:21:46.9 and Dec. = -59:51:42 (5 arcseconds uncertainty). This position is consistent with that of HD 306414, which confirms that the B supergiant proposed in ATel #470 is the counterpart for IGR J11215-5952. Please see Steeghs et al. (2006) for more information: ATel 768 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #136March 20 2006 | Smith et al. (2006, ATel #766) report on their observation of the superfast X-ray transient (SFXT) IGR J11215-5952 with RXTE. Based on the recurrence period of ~330d reported earlier by Sidoli et al. (2006, astro-ph/0603081), the authors proposed monitoring the source with RXTE during its next outburst which was expected to take place on March 15-18, 2006. As expected, an outburst was recorded by RXTE from March 16-17, which the authors used to derive a period of 329.0d between outbursts. This is the first confirmation of a recurrence period in a SFXT candidate. When the outburst is over, the authors will issue another ATel. The RXTE/PCA data show extreme variability, a hard spectrum (gamma=-1.7(2)) in 2.5-15 keV consistent with either a BHC in a hard state or an accreting pulsar, and a column density of 11(3)x1022 atoms/cm2 (higher than expected from galactic absorption alone). These characteristics are typical of SFXTs in outburt. The unabsorbed flux at the peak of the outburst is 2x10^-10 ergs/cm2/s in 2-10 keV, which corresponds to 1036 ergs/s assuming the distance of 6.2 kpc which Masetti et al. (2005, astro-ph/0512399) derived for the possible optical companion HD 306414. If the association with HD 306414 holds, then the longer orbital periods of SFXTs could help explain why they are different from persistent X-ray binaries. More details can be found in Smith et al. 2006: ATel 766 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #135March 06 2006 | In a recently accepted letter, Sidoli et al. 2006 report some results on the INTEGRAL source IGR J11215-5952: 1. they discover two new outbursts of this source, and report their spectral analysis on 5-100 keV. These outbursts are of longer duration than typical outbursts observed to date from other Supergiant Fast X-ray Transients (SFXTs), and they suggest a periodicity of 330 days (or half of it). 2. they confirm the association of this high-energy source with the HD 306414 optical counterpart (consistent with the error circles of the 3 outbursts). 3. they confirm that this source belongs to the newly discovered class of Supergiant Fast X-ray Transients. This discovery of recurrent outbursts, and the suggestion of a possible periodicity, could confirm the hypothesis that SFXTs are HMXBs in wide orbits. More details can be found in Sidoli et al. 2006, accepted for publication in A&A, astro ph 0603081 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #134March 02 2006 |
The transient source IGR J17419-2802, which has recently become active, was observed in radio frequencies using the VLA on Feb. 26, 2006.
Rupen et al. (2006, ATel 755) did not find a single point source of radio emission within the Swift XRT error circle revised by
King (2006, ATel 745). This region was also observed in October, 2005, with no radio detections.
More information about these observations can be found in Rupen et al. (2006, ATel 755). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #133Feb 23 2006 |
Grebenev et al. (2006) report that the transient source IGR J17419-2802 became active during
INTEGRAL Open Program observations of the Galactic Center. The source was seen in the ISGRI energy range 18-45 keV with an
average flux of 7.7+/-0.6 mCrab with a significance of ~12.
Additionally, the X-ray position of the source has improved to (J2000) R.A. = 17h41m56.0s and Dec. = -28:01:54.5 (error ~ 3.5") thanks to a reanalysis of a SWIFT XRT observation from October, 2005. This position is about 5.5" from the previously reported XRT position with a single candidate from the 2MASS catalog inside the new error circle. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #132Feb 6 2006 | Masetti et al. (2006) ATel 719, report on some optical observation of IGR J13091+1137 with the 1.5m telescope of the Astronomical Observatory of Bologna. The authors mention that the spectral continuum is typical of a normal spiral galaxy, with severa absorption lines and a weak NII emission. All of these features are at a redshift z = 0.025. Masetti et al. discuss and compare their results with the X-ray properties of the source and conclude that IGR J13091+1137/NGC 4992 is a X-ray bright, Optically normal galaxy, also an heavily obscured AGN. This is the first of this type (XBONG) ever detected above 20 keV More details can be found in Masetti et al. 2006 ATel 719 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #131Feb 1 2006 | Masetti et al. (2006) report the possible association of the symbiotic star CD-57 3057 with the INTEGRAL source IGR J10109-5746. They first remark that the Swift source SWIFT J1010.1-5747 is tyhe likely X-ray counterpart to the INTEGRAL source, which gives an improved X-ray position of RA=10 11 03.0 DEC=-57 48 14.7 (+-4.3 arcsec) With this improved position the author identify CD-57 3057 as the optical counterpart to the X-ray source. According to Masetti and colleagues IGR J10109-5746 is a system similar to IGR 12349-6434/RT Cru, which lead them to conclude that IGR J10109-5746 is also a symbiotic system. More details can be found in Masetti et al. 2005 ATel 715 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #130Jan 30 2006 |
IGR J00234+6141: Halpern & Mirabal (2006 ATel 709)
report on the probable identification of the optical counterpart to
this faint hard X-rays source.
Its location at
R.A. = 00h 22m 57.63s,
Decl. = +61o 41' 07.8" (J2000),
is only 6" from possible ROSAT counterpart to the INTEGRAL source proposed
by den Hartog et al. (2005, ATel 394), makes it a secure counterpart of the
ROSAT source.
The optical source shows emission lines in the Balmer series. The magnitudes reported
are B=18.01, R=16.34, I=15.63, J=15.12, H=15.05, K=14.77.
According to Halpern and Mirabal all properties of this star are typical of X-ray emitting
cataclysmic variables.
More details on their observations and the associaition of this star with the
Xray objects are presented in
ATel 709
IGR J16358-4726: Mereghetti et al. 2006 (accepted in A&A) reporting on their XMM observations of SGR 1627-41, report also some results of IGR J16358-4726 that lies nearby. The source was detected on 2 occasions. The spectra are well described with an absorbed power law with Gama=1.5 and Nh=2e23 cm-2 (for the brightest observation). During the same observation the 5880s pulsation is present although the source flux is 200 times dimmer than when the pulsation has been discovered with Chandra. The author also report than in subsequent observations the source is not detectd with an upper limit on the 2-10 keV flux of 4e-14 erg/cm2/s. More details can befound in Mereghetti et al. 2006 astro-ph 0512059 H1743-322/IGR J17464-3213 Remillard et al., 2006, ApJ, 637, 1002, report on the analysis of RXTE data of this source during its 2003 outburst. They focus on timing analysis and search for high frequency QPOs. The authors first report the detection of a QPO at 239 Hz consistent with previous finding. While grouping the data they identify QPOs at: 166 Hz (group with higher flux) and 242 Hz (group with lower flux) . The ratio of the two feature is 1.46 consistent with the 3:2 ratio found in other BH binaries. The authors compare the behaviour of the source with other known BH binaries, and discuss these results in the context of models of QPOs. More details can be found in Remillard et al. 2006 ApJ, 637, 1002 IGR J00370+6122: den Hartog et al. 2006 (accepted in A&A) report on their survey of the Cassiopea region, in which lies the IGR source. Reanalysing their data, the authors refine the position to 0h 37m 07.3s dec= +61¡ 21' 50" (+- 2' at 90% confidence) This further suggests that 1 RXS J003709.6+612131 is the soft X-ray counterpart to the source. They also use RXTE to measure the ephemeris of the source along its orbital period. Their analysis further associates the IGR and Rosat sources. Reanalysing archival Beppo SAX data, den Hartog et al. report that the source was detected in 4 occasions. The brightest observation lead to a spectral fit with a power law of photon index 2.6. RXTE ToO lead to power law shaped spectra with gamma=2.74. Comparison between INTEGRAL, Beppo-SAX and RXTE show that the source is highly variable from orbit to orbit. The Nh as measure by RXTE and Beppo-SAX varies from 7e22 to 13e22, while the measured flux vary from 3e-10erg/s/cm2 (2-20 keV) to 1.8e-11 erg/s/cm2 (3-30 keV). All this confirms the HMXB nature of the source. More details (and mention of IGR J00234+6144) can be found in den Hartog et al. 2006 astro-ph 0601644 IGR J17091-3624: Capitanio et al. 2006 (accepted by ApJ) report on RXTE and INTEGRAL observations of IGR J17091-3624. These authors have have cumulated/fitted the observations as followed: 1st epoch ISGRI+RXTE/PCA 2nd epoch JEMX+ISRI 3rd epoch ISGRI; From this they first confirm the low absorption (Nh<1e22cm-2) While the first epoch can be fitted by a comptonised spectrum, the second shows the presence of a bright thermal component in the soft X-rays. These authors analyse the differences as due to ta transition form a hard state to a soft state. During the 3rd epoch, the spectra can be fitted with a comptonised model whose parameters are similar to that of epoch 1. They interpret this as a transition back to the hard state. The authors discuss their findings, and compare this source to another X-ray transient and Black Hole candidate H 1743-322/IGR J17464-3213. Amongst other similarities, the authors mention the relatively low temperature (~20 keV) of the comptonising electrons. They further discuss the nature of the compact object, although they cannot draw conclusions as to whether it is a neutron star or a back hole. More details in Capitanio et al. 2006 astro-ph 0601503 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #129Jan 16 2006 |
Halpern and Gotthelf (2006)
report that IGR J18450-0435 and AX J1845.0-0433 are likely to be the same source, even though the refined
ASCA position of R.A.=18h 45m 02.1s, Dec.=-04d 33' 55" (J2000, uncertainty of 12") and of its optical counterpart
(R.A.=18h 45m 01.59s, Dec.=-04d 33' 56.5") lie 2.4' and 2.3' away from the Bird et al. (2006) position, respectively,
or outside the 1.8' error radius of Bird et al. (2006). There are no other ASCA sources near the IGR source, and the mean
flux reported by Bird et al. (2006) is within the range of ASCA values measured during quiescent and flaring periods.
Their results are described in Halpern & Gotthelf (2006): ATel 692 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #128Jan 10 2006 | Mukai et al. (2006) report on result of observation of of the recently found IGR J14536-5522 with Swift. They first mention the positional coincidence of the IGR source with that of the BAT survey source Swift J1453.4-5524 which suggests the sources are the same. They find a moderately bright (3.3e-11 ergs/cm^2 s keV in 0.4-10 keV) source with the XRT at RA = 14h53m41.7s, dec=-55d21m42.8s, This position is also coincident with the ROSAT all sky survey source 1RXS J145341.1-552146. According to Mukai et al. the X-ray spectrum requires at least two components to be fitted: a hard power law (with photon index ~ 1.0) and a soft blackbody (kT~70 eV) with little absorption, The authors further discuss the type of the object and mention that this kind of spectrum is reminiscent of certain magnetic cataclysmic variables. There is apparently a single bright UVOT source at magnitude 17.59+/-0.02 in the UVW1 filter, at RA=14h53m41.1s, dec=-55d21m46s, which does not appear to be variable, while the soft X-ray source is highly variable. More details can be found in Mukai et al. (2006) ATel 686 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #127Jan 06 2006 |
Based on the Swift position and potential optical counterpart to IGR J01583+6713 provided by Kennea et al. (c.f. Mail #124, ATel:673),
Halpern & Tyagi (2005) report a Be counterpart with magnitudes B=14.98, R=13.24, and I=12.12. This star is located 2.8" away
from the Swift position at R.A. = 01h 58m 18.44s and Dec. = +67d 13' 23.5" (J2000), or within Swift's 3.5" error radius. A low-resolution
optical spectrum reveals strong H-alpha (EW ~ 7 nm) and weak H-beta (EW ~ 0.6 nm) emission lines, as well as diffuse interstellar bands,
which are typical spectral features for Be/X-ray binaries.
Halpern & Tyagi (2005) also propose an optical counterpart to IGR J06074+2205 in ATel:682. The Be star is at R.A. = 06h 07m 26.6s and Dec. = +22d 05' 48" (J2000), or within an arcminute of the JEM-X position, with magnitudes from the USNO A2.0 and 2MASS catalogs of B=13.3, R=12.1, J=10.49, H=10.19, and K=9.96. An H-alpha emission line (EW ~ 0.7 nm) and diffuse interstellar absorption bands are present which suggest a Be/X-ray binary.
Please read ATels:681-682 for more information: Finally, Kuiper et al. (2005) have discovered 4 new sources in the Circinus and Carina regions with ISGRI. For each source, they provide a J2000 position, a flux between 20-65 keV and they discuss potential counterparts. IGR J10101-5654 has the position R.A. = 10h 10m 08s and Dec. = -56d 54' 46" (2.2' error radius), a flux of ~1.4 mCrab with no known counterparts. However, it is within the 2-sigma position contour of the high-energy gamma-ray source 3EG J1014-5705. IGR J14515-5542 is at R.A. = 14h 51m 33, Dec.= -55d 42' 16" (3.2' error radius), with a flux of ~ 1.7 mCrab, and is located near 1RXS J145132.4-554041/LEDA 3079667. IGR J14536-5522 is located at R.A. = 14h 53m 38s and Dec. -55d 22' 23" (2.3' error radius), a flux of ~2.3 mCrab, and its potential counterparts are 1RXS J145341.1-552146 and 1RXS J145349.4-552144. IGR J16351-5806 has the coordinates R.A. = 16h 35m 10s and Dec. = -58d 06' 04" (3.2' error radius). The flux is about 3.1 mCrab with LEDA 58547/ESO 137-34 (Sey-2) as the counterparts. Optical observations are underway for IGR J10101-5654, IGR J14515-5542, and IGR J14536-5522.
More information can be found in ATel:684: | 2005 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #126Dec 22 2005 | Wen et al. 2006 (accepted in ApJS) report on their systemtatic search for periodicities in 8.5 years data of RXTE/ASM, for 458 sources. Among those they report (confirm and refine) the detection of pulsations at 15.670 days for IGR J00370+6122, 52.36 days for IGR J11435-6109, 13.552 days for IGR J19140+0951, They present their technic for the period search, and briefly discuss their findings for each sources. More details can be found in Wen et al. 2006 accepted in ApJS, astro-ph0512529 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #125 Dec 16 2005 | Masetti et al. 2005 (accepted in A&A) present optical spectroscopy of several more IGR sources in addition to those presented in an earlier work (c.f. Mail #116, astro-ph/0511182). The authors confirm that IGR J10404-4625 and IGR J16482-3036 are AGNs, as was previously suggested by Bassani et al. (2005, c.f. Mail #89, ATel #537). IGR J10404-4625 is associated with the emission-line galaxy LEDA 93974 (z=0.0237), and IGR J16482-3036 has a redshift of z=0.0313. Possible optical counterparts are proposed for IGR J11215-5952 (=HD 306414 ?), IGR J11305-6256 (=HD 100199 ?), and IGR J16207-5129 (=HD 146803 ?), which are consistent with them being Galactic HMXBs. Based on the multi-wavelength spectrum of each source, the physical parameters for these objects are discussed further in: astro-ph0512399 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #124 Dec 13 2005 | Kennea et al. 2005 (atel 673) report on follow up observations of IGR J01583+6713 with Swift. During a 5 ks observation of the field they identify a single point source at: RA = 01:58:18.2, Dec = +67:13:25.9 +- 3.5 " (90% containment) A J=11.5 2MASS catalogue object is 2.9 arcseconds from the XRT position. This object is also present in the USNO catalogue, with reported magnitudes of R=13.9 and B=15.3 The authors report spectral analysis showing that the spectrum is consistent with an absorbed power law with N_H~10^23 cm-2. Interestingly the auhors report that the system does not appear to be fading. More details in Kennea et al. 2005 ATel 673 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #123 Dec 13 2005 | Albert et al. 2005 report on observations of HESS J1813-178/IGR J18135-1751 with the MAGIC Cherenkov telescope. They report the detection of a source at RA=18h 13m 27s dec=-17h 48' 40" (+- 2') coincident with the HESS source. They present a spectral analysis of their observations. The 500-8000 GeV spectrum is (coinsistent with the spectrum obtained by HESS) fitted with a simple power law with a photon index Gamma=2.1 The authors discuss their result and include them in a multiwavelength view. In this respect they compare their data with different models of emission and discuss the results obtained. They point out the difficulty of including the INTEGRAL data in the mutliwavelength fits, which may indicate a second population of electrons. More details can be found in Albert et al. 2005 astro-ph 0512283 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #122 Dec 12 2005 | Steiner et al. 2005 announce the discovery of a new X-ray transient IGR J01583+6713. The source was discovered in a 130-ks mosaic image of the 20-40 keV band from IBIS/ISGRI during an open-program observation of the Cas A region on Dec. 6-7, 2005. It has the coordinates (RA;Dec) = (29.57;+67.22) with an uncertainty of 2 arcminutes. The average source flux (20-40 keV) from the mosaic image is 14 mCrabs at a significance of 13 sigma. IGR J01583+6713 is not detected in individual pointings lasting ~3 ks, nor in the 40-80 keV energy band with an upper limit of 7 mCrabs. The source was always outside the field of view of JEM-X. In a 50-ks mosaic image (20-40 keV) of the next spacecraft revolution, the source flux is 11 mCrab at the 8-sigma level. However, the source flux decreased to 8 mCrabs with a significance of 5.5 sigma in a mosaic image (20-40 keV) of the remaining 150 ks of that revolution, i.e. the decrease occured over a timescale of days. There are no X-ray counterparts within the ISGRI error circle according to Simbad. The closest known X-ray source is 1RXS J015918.4+671807 which is 7.7 arcminutes away. ATel 672 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #121 Dec 5 2005 | Bassani et al. 2005 , (A&A in press) present a sample of 62 AGN candidates detected during analyses of over 11,000 ISGRI pointings in the 20-100 keV range. Of these sources, 42 are classified as Seyfert galaxies (23 of type 1-1.5, and 19 of type 2), 6 are blazers, and the remaining 14 are still unclassified. Intrinsic photoelectric absorptions larger than 10^22 atoms/cm2 are reported for roughly 65% of the sample. Thirty-two objects were already listed as candidate or confirmed AGNs in the catalog of Bird et al. (2005). This work adds 30 new AGN candidates, 4 of which Bird et al. (2005) listed as unidentified (IGR J07565-4139, IGR J14492-5535, IGR J16194-2810, IGR J16558-5203). The other new AGN candidates are IGR J12026-5349, IGR J12415-5750, IGR J13000+2529, IGR J13057+2036, IGR J14552-5133, IGR J16119-6036, IGR J17204-3554 (a possible molecular cloud in Bird et al., 2005), IGR J18249-3243, IGR J20187+4041, IGR J20286+2544, and IGR J21178+5139. Their results are described in: astro-ph0512015 During an XMM-Newton observation of SGR 1627-41, Mereghetti et al. (2005, A&A in press) detected IGR J16358-4726 serendipitously. The source exhibited its lowest recorded flux (5.4x10^-13 ergs/cm2/s in the 2-10 keV range), which is a factor 5 lower than the flux during previous detections by ASCA and BeppoSAX (Patel et al., 2004). An absorbed power law yields a photon index of 1.3 and a column density of 2x10^23 atoms/cm2, but the low count rate did not constrain the spectral parameters, and the long pulsation of ~5580 s (Patel et al., 2004) could not be detected. Details are available in: astro-ph 0512059 Finally, Pandey et al. (2005, A&A in press) report on radio observations of 40 IGR sources taken with the GMRT. There are radio counterparts in the ISGRI error circles of 24 IGR sources. Seventeen galactic and 7 extragalactic sources were identified based on their radio emission. Three unresolved sources (IGR J17303-0601, IGR J17464-3213, IGR J18406-0539) are likely radio-emitting X-ray binaries and thus possible microquasar candidates. The extended nature of the radio emission within the error circles of IGR J17195-4100, IGR J17200-3116, and IGR J17456-2901 suggests that they are extragalactic in origin. Five sources (IGR J16207-5129, IGR J16558-5203, IGR J17285-2922, IGR J17460-3047, IGR J18450-0435) display radio emission typical of extended galactic sources, although their location in the Norma Arm region means they are likely to be galactic. This suggests that these sources could belong to a new class of extended galactic radio emitters. Six sources (IGR J16167-4957, IGR J16195-4945, IGR J16393-4643, IGR J17252-3616, IGR J17254-3257, IGR J17475-2822) present diffuse radio emission, but the radio emission is not associated to IGR J16393-4643, IGR J17456-2901, IGR J17460-3047, and IGR J17475-2822 because of their crowded fields. There are no GMRT counterparts for six sources (IGR J00370+6122, IGR J01363+6610, IGR J16358-4726, IGR J17488-3253, IGR J18027-2016, IGR J18490-0000). More information can be found in: astro-ph 0512060 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #120 November 30 2005 | in't Zand et al. 2005 , in a recently accepted paper, in't Zand et al. (2005) report the results of their observations of IGR J19140+0951 with Chandra and Optical follow ups. 1st of all the Chandra observation allows them to give the most precise X-ray position to the source to date: RA = 19h 14m 4.232s dec = +09o 52' 58.29" (+- 0.6") a position consistent with measurments from INTEGRAL, EXOSAT and Beppo-SAX The authors present a spectral analysis of these data; the X-ray spectrum of the source is well fitted with an absorbed power law with Gamma 1.1 +- 0.8 and Nh=1e23 cm-2, consistent with previous analysis. The 1-10 keV unabsorbed flux is 1.5e-10 erg/cm2/s, which is lower than any of the INTEGRAL observations but brighter than all the RXTE observations presented in former studies. The authors do not confirm the presence of an iron line. A possible pulsationat 6.5 ks is reported although confirmation is needed. The X-ray position allows in't Zand et al. 2005 to identify a possible IR counterpart in 2 MASS (2MASS J19140422+0952577) Using the NTT they refine the position of this object to RA=19h 14m 4.231s Dec=9¡ 52' 58.35" (0.06" from the X-ray position) They obtained spectra of this source in optical using the William Herschel telescope. The spectrum comes out of absorption above 7000 Œ. The photometry in V, I, Ks points to an extinction towards the source Av~11 consistent with the interstellar extinction. They report magnitudes Ks~8.7, I~13.0, V> 18.8 The authors discuss their results and the possible type of the system, and by analogy with another IGR source suggest the system is a peculiar higlhy redenned object. They give preference to a scenario in which the companion is a early type star in an HMXB. More details can be found in in't Zand et al. accepted in A&A astro-ph 0505256 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #119 November 24 2005 | Kuiper et al. 2005 , ATel 662 reports on the results of observations of the Cassiopeia region with INTEGRAL. Besides other sources, they mention in particular the detection of a new source IGR J02097+5222, at position R.A.= 02 09 45.6, Decl. = 52 22 48.0 (+-3 arcmin). The authors report that this position is consistent with that of 1E 0206.3+5212, a Seyfert-1 galaxy at z=0.0492. As pectrral fits to their data with a model consisting of a powerlaw yielded to a power law photon index Gamma=1.7+/-0.4 and a 20-65 keV flux of (9.7 +/- 1.4)E-6 ph/cm2 s keV More details can be found in Kuiper et al. 2005 ATel 662 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #118 November 15 2005 | Rodriguez, Bodaghee et al. 2005 , in a paper accepted in MNRAS, report on the results of simultaneous INTEGRAL and XMM observations of the X-ray pulsar IGR J16320-4751. We start by refining and improving the X-ray position to RA=16h 32m 01.9s DEC= -47deg 52' 27" with an uncertainty of ~3" at 90% confidence. This allows us to discriminate between the 2 possible infra red counterparts we had suggested in a previous work. Our simultaneous coverage allows us to confirm the presence of X-ray pulsations at ~1300 s, that we detect above 20 keV with INTEGRAL for the first time. The pulse fraction is consistent with being constant with energy, which is compatible with a model of polar accretion by a pulsar. We study the phase resolved spectroscopy, and show that the pulse is solely due to variations of the X-ray flux emitted by the source and not to variations of the spectral parameters. We detect a soft excess appearing in the spectra as a blackbody with a temperature of ~0.07 keV, and a narrow iron line at ~6.4 keV. While our results are compatible with IGR J16320-4751 being a pulsar/HMXB, we further discuss the origin of the X-ray emission in this object: the hard X-rays are likely the result of Compton emission produced in the close vicinity of the pulsar. Based on energy argument we suggest that the soft excess is likely the emission by a collisionally energised cloud in which the compact object is embedded. More results in Rodriguez et al. 2005 accepted in MNRAS astro-ph 0511429 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #117 November 10 2005 | Kuiper et al. 2005 Atel 654 report on the results of their Chandra observations of the field around IGR J16493-4348. They find a single point source located at R.A. = 16 49 26.92, Decl.= -43 49 8.96 (+- 0.6" at 90%), that they associate with the afore mentioned IGR source. This position puts the source at about 1.2 arcmin from PSR J1649-4348, from which no photons are detected. They found a candidate couterpart in the 2MASS catalogue, 2MASS J16492695-4349090, with J,H and Ks magnitudes of 14.59, 12.86 and 11.94 respectively. They also report an identification from NTT/Sofi observations leading to a magnitude Ks=12.0 consistent with the 2MASS result. This show the source s not extremely variable in this band. Thenon detection of Optical counterpart may indicate strong absorption. The authors suggest the source is an heavily absorbed XRB. More details in Kuiper et al. 2005 Atel 654 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #116 November 8 2005 |
Masetti et al. 2005 (astro-ph/0511182) present optical spectroscopy of the optical counterpart candidates of several hard X-ray sources,
among them IGR J18406-0539, IGR J19473+4452, as well as another source (LEDA 170194) which the authors refer to as IGR J12391-1610. The authors
report that IGR J12391-1610 and IGR J19473+4452 are Seyfert 2 galaxies at redshifts of 0.036 and 0.053, respectively. Associated with SS 406,
IGR J18406-0539 is a Be X-ray binary located at a distance of 1.1 kpc. Their multiwavelength analyses enable the authors to elaborate on the
physical parameters of these objects.
In addition, Sazonov et al. 2005 (astro-ph/0508593) report on Chandra observations of 8 INTEGRAL sources. Six of these have a bright object within the ISGRI error circle. Of these, 5 have been associated with nearby galaxies implying they are AGNs, and the other is likely a high-mass X-ray binary of the LMC. Of the AGNs, 4 have redshifts between 0.025 and 0.055. The X-ray spectra of the AGNs present significant absorptions (10^22 < nH < 10^24 atoms/cm2). More results are described in Masetti et al. and Sazonov et al. (2005, A&A in press) which are now available on astro-ph: astro-ph/0511182 astro-ph/0508593 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #115 November 4 2005 | Zurita Heras et al. 2005 (astro-ph/0511115) present our analysis of IGR J17252-3616 using observations by INTEGRAL and XMM-Newton. The source is persistent with an average count rate of 6.4 mCrab in ISGRI's 20-60 keV energy band. The refined X-ray position from XMM-Newton is R.A.(J2000)=17:25:11.4 and Dec.=-36:16:58.6 with a 4" error radius. Located 1" away, 2MASS J17251139-3616575 is the lone infrared counterpart (Ks-band magnitude =10.7). A spin period of 413.7 s and an orbital period of 9.72 days were discovered. The source spectrum is heavily-absorbed (nH~1.5x1023 atoms/cm2), and can be represented by a flat power-law (Gamma~0.02,Ecut~8.2 keV) or a Comptonized model (kTe~5.5 keV, tau~7.8). An iron K-alpha line is clearly detected at 6.4 keV. The phase-resolved spectrum displays no changes other than in the flux that is emitted. IGR J17252-3616 and EXO 1722-363 can be considered as the same source due to the common spectral and timing features. These observations suggest that IGR J17252-3616 is a wind-fed accreting pulsar with a supergiant companion. Our results are described in Zurita Heras et al. (2005, A&A in press) which is now available on astro-ph: astro-ph/0511115. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #114 November 3 2005 | Corbet et al. 2005 (ATel #649) report on the discovery of an orbital period for the heavily-obscured pulsar IGR J16320-4751. A Swift/BAT light curve from Dec. 12, 2004, to Sep. 15, 2005, reveals a strong modulation with a period of 8.96+/-0.01 days. Combined with its pulsation period of ~1300s (Lutovinov et al., 2005), the source's location on the Corbet diagram suggests that the system consists of a neutron star accretor with an early type supergiant companion. Their results are described in ATel #649. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #113 October 28 2005 | Gotz et al. 2005 accepted in A&A, report the discovery of five new sources in the direction of the LMC with IBIS/ISGRI. The sources are IGR J03532-6829, J05009-7044, J05319-6601, J05346-5759 and J06239-6052. The are respectively located at RA= 03h 53m 14s dec=-68deg 29' 00" RA= 05h 00m 59s dec=-70deg 44' 45" RA= 05h 31m 57s dec=-66deg 01' 35" RA= 05h 34m 35s dec=-57deg 59' 35" RA= 06h 23m 58s dec=-60deg 52' 15" (+- 3.5') The authors futher discuss their type, and location. They suggest J05319-6601is associated with the LMC, given that there are sevral known X-ray sources within the error it is possible that it is the result of belended emission from those. J05009-7044 is probably the same as J05007-7047 a possiblle HMXB, but the authors also say that in the ISGRI error box lies a radio emitting Galaxy All other sources are not coincident with the LMC: J05346-5759 is spatially coincident with TW Pic, a CV; and J03532-6829 can be associated with 1 RXS J 035257.7-683120, a probable AGN, while J06239-6052 is coincident with SUMSSS J062346-605222 a radio galaxy, which makes it an AGN candidate. More details can be found in Gotz et al. 2005, astro-ph 0510770 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #112 October 25 2005 | Smith et al. 2005 accepted for publication in ApJ report on X-ray observations made with RXTE and Chandra, as well as INTEGRAL. They refine and imprve the position of the source to RA =17h 39m 11.58s, dec=-30deg 20' 37.6" which allowed them to search for an optical cointerpart of the system. They identify a bright star from the USNO B1.0 cat USNO BA.0 0596-0585865, with R=1131.6 and B=17.32 (first epoch). Thisstar is also a bright 2 MASS source (SMASS J17391155-3020380) with J=8.6, H=7.82, K=7.43. The authors report that during both low level and outburst states the high energy spectra of the source is hard. The absorption column density is seen to vary fro mone outburst to another. The optical spectrocsopy presented in the companion paper (see below) suggest the companion is a supergiant star. the combination of those results lead Smith and collaborators to define a class of Supergiant Fast Xray Transient, a number of which has been recently deiscovered. More details are available in astro-ph 0510658 Neguerela et al. 2005 accepted in ApJ present the spectroscopy and photometry of the optical counterpart of IGR J17391-3021 /XTE J1739-302. They identify the star as a O8 Iab(f) supergiant located at 2.3 kpc. The authors discuss the peculiarities of this new class of sources (e.g. the variable absorption column density), and compare them with other known High mass systems. More details in astro-ph 0510675 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #111 October 19 2005 | Torres et al. 2005 in ATel #634, confirm the NIR counterpart to IGR J17473-2721 (=XTE J1747-274) that was initially proposed by Juett et al., 2005 (ATel #521). Their observations consist of a series of Ks-band images with a cumulative exposure time of 375 s. These images show a single point-like source located 0.3-0.4 arcsec away from the position of the NIR candidate suggested in ATel #521. The authors associate this source with a field star that made the counterpart appear extended during its outburst. Therefore, the proposed counterpart has dimmed significantly and is not detected at the 3-sigma upper limit magnitude of Ks>17.4. They conclude that the drop in luminosity as compared to when the transient was in outburst confirms it as the NIR counterpart to IGR J17473-2721. More details can be found in Atel 634 (Torres et al.) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #110 October 17 2005 | Tuerler et al. 2005 2005 Atel 631 report on the preliminary results of an 50 ks INTEGRAL ToO on IGR J17269-4737 / XTE J1727-476. The source hass a flux of 15 mCrab in the 3-10 keV range covered by JEM-X, and is not detected at higher energy nneither by JEM-X nor by ISGRI. The 3 sigma upper limit is 4mCrab in the 20-40 keV energy range. According to Türler and collaborators, the source has a very soft spectrum well fitted by a by a black body model with kT=0.37 keV. A thermal bremsstrahlung fits the data equally well, with kT=0.55 keV. The 3-10 keV flux is about 2e-10 erg/cm2/s. Kennea et al. 2005 Atel 632 report on analysis of a Swift XRT follow up observations and reanalysis of the observation reported in their Atel #626. The latest obs. leads to Nh=4.8 e21 cm-2 and kT=0/91 keV for a model of bremsstrahlung. Comparing this observation with tthe (reanalysis) of the previoous, they find a drop in flux of about 60%. A disk blackbody model also represents the data well. In this case kT= °.53 keV. This model suggests the source is a black hole transient. The authors further discuss the difference between their results and those from INTEGRAL. More details can be found in Atel 631 (Tuerler et al.) and Atel 632 (Kennea et al.) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #109 October 14 2005 | Bassani et al. 2005 accepted for publication in ApJ Letters, report on the results of their high energy analysis of the field of IGR J17204-3554. These authors discuss the possible association of IGR J17204-3554 wih the molecular cloud NGC 6334. They say that the gamma ray emission detected from this direction makes it very likely that IGR J17204-3554 is a high energy source embedded or located behind the cloud. Bassani et al. also report follow up observations of the source with Swift and Chandra. They found an extragalactic object which has the required characteristics to explain the gamma ray emission. The Chandra/IBIS spectrum is well fitted by a model of an absorbed power law with Nh 1.4e23 and Gamma=1.2 More details can be found in Bassani et al. astro ph 0510338 The HESS collaboration report the results of the survey of the inner part of the Galaxy at very high eenergy. They discuss the possible associations of 2 sources with IGRs. Namely IGR J16320-4751 with HESS J1632*478, and IGR J16358-4726 with HESS J1634-472. For the former the authors say that the extension of the HESS source does not plead in favor of the association,. In the second case, the author just mention that the offset between tthe IGR and the HESS source renders the association unlikely. In both cases however the association is not completely ruled out. More details in Aharonian et al. accepted for publication in ApJ, astro ph 0510397 Concerning IGR J17269-4737, Steeghs et al. Atel 629 report on the near infra red imaging of the field containing the source. They detect a Ks=16.2 source coincident with the I counterpart reported by Maitra et al. in Atel 628, at a position : R.A.=17:26:49.30, Dec=-47:38:25.5 A finding chart is also available, and will be put on the IGR sources pages. More details can be found in Steeghs et al. Atel 629 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #108 October 13th 2005 | There are several announcements concerning the new source IGR J17269-4737 (a.k.a. XTE J1726-476) co-discovered by RXTE and INTEGRAL (c.f. ATels 623, 624). First, Kong (ATel:625) reports a Swift XRT position of R.A.=17:26:50.2 and Dec.=-47:38:26 (6" uncertainty) which is about 1.2' away from the INTEGRAL position. Furthermore, Kennea et al. (ATel:626) also provide a Swift XRT position of R.A.=17:26:49.8 and Dec.=-47:38:23.2 (8" uncertainty) that is consistent with the Swift position of Kong (ATel:625) and is also about 1.2' away from the ISGRI position. Although the Swift position is almost 7' away from the XTE position (ATel:623), there are no sources in the XTE error box leading the authors to conclude that the IGR and XTE sources are indeed the same. Kennea et al. remark that a thermal bremsstrahlung model (kT=1.58+/-0.03 keV) provides a better fit than a simple power law. The nH value they derive (~3x1021 atoms/cm2) is equivalent to the galactic absorption along the line of sight. Between 0.2 and 10 keV, the absorbed and unabsorbed fluxes are 1.75x10^-9 erg/s/cm2 and 3.75x10^-9 erg/s/cm2, respectively. This corresponds to a 0.2--10 keV luminosity of 3.8x1038 erg/s assuming a distance of 8.5 kpc. The source was outside of the field of view of Swift's optical camera. However, Maitra et al. (ATel:628) used the refined Swift position to locate an optical counterpart (new to the DSS) at R.A.=17:26:49.28 and Dec.=-47:38:24.9 (0.3" uncertainty). More details in ATels 625, 626 and 628: Atel 625 Atel 626 Atel 628 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #107 October 10 2005 | This report to notify the discovery of a new source approximately at the same time both by INTEGRAL and RXTE. Tuerler et al. Atel 624 report the detection of IGR J17269-4737 with ISGRI on october 6-7 at RA=261.72, DEC=-47.622 in the 20-40 keV range (3.8 arcmin error) while Levine et al. Atel 623 report the detection of XTE J1727-473 with the ASM (1-12 keV) on october 4 at ra=261.585, dec=-47.570 (0.7 degree uncertainty). They also mention an increase of flux between successive observations. The proximity of the two position probably indicates the XTE and INTEGRAL sources are the same. More details in Atel 623 and Atel 624 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #106 October 4th 2005 | A Swift ToO observation of IGR J17419-2802 (c.f. mail #105) has improved the source position to R.A. = 17:41:56.4 and Dec. = -28:01:53.0 (J2000), with an uncertainty of 8". This position is about 27" away from the center of the 2' ISGRI error circle given by Grebenev et al., 2005 (ATel #616). Two objects from the 2MASS catalog lie inside the XRT error box. The absorbed flux remained constant at 3.6x1011 ergs/cm2/s with no sign of variability during 2ks of exposure in a 5.5 ks observation. A power law fits the spectrum well with nH=(1.4+/-0.3)x1022 atoms/cm2 and a photon index of 1.6+/-0.3. The results of Kennea et al., 2005, are described in Atel 617 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #105 October 3rd 2005 | Grebenev et al. 2005 (Atel 616) report on the discovery of a new source IGR J17419-2802, with ISGRI during deep observations of the GC, on Sept 29th. The source position is R.A.=17h41m55s, Decl.=-28d02m13s (uncertainty 2') Preliminary analysis showed that it had a power law spectrum, with Gamma~3.2 More details in Grebenev et al. (2005) Atel 616 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #104 September 29th 2005 | Bodaghee et al. 2005 (accepted for publication in A&A) present their analysis of INTEGRAL and XMM-Newton observations of IGR J16393-4643 (a.k.a. AX J163904-4642). The source is persistent in the 20--40 keV band at an average flux of 5.1x10^-11 ergs/cm2/s with variations in intensity by at least an order of magnitude. A pulse period lasting 912+/-0.1 s is detected in both the ISGRI and EPIC light curves. The source spectrum, whose shape does not change with the pulse, features a large intrinsic absorption (nH=2.5x1023 atoms/cm2) and a cutoff above 10 keV, but a Compton thermalisation model can also be applied. Iron lines are apparent at 6.4 and possibly 7.1 keV, with a soft excess emission (7x10^-15 ergs/cm2/s) between 0.5 and 2 keV. The authors conclude that the source belongs to the class of heavily-absorbed, wind-accreting X-ray pulsars. The refined X-ray position derived from EPIC is R.A. (J2000) = 16:39:05.4, Dec. = -46:42:12 (4"error) which places the source about 1' away from 2MASS J16390535-4642137. Their results are described in Bodaghee et al., 2005, to be published by A&A, and appearing soon on astro-ph. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #103 September 23th 2005 | Pandey et al. 2005 (accepted for publication in A&A) report the results of their search for counterparts of IGR sources using the GMRT radio telescope. They report the detection of possible radio counterparts for 7 of them, namely J06074+2205, J15479-4529, J16479-4514, J17091-3624, J18027-1455, J18539+0727 and J21247+5058 Pandey et al. also report observation, although with non detection of 10 additional sources, namely J16316-4028, J16318-4848, 16320-4751, J16418-4532, J17391-3021, J17544-2619, J17597-2201, J18325-0756, J18483-0311, J19140+0951. For these sources 3 sigma upper limits at 0.61 GHz and/or 1.28 GHz are given. For the sources with possible identification in radio, the authors discuss the origin of the source and suggest that the morphology of IGR J16479-4514 is that of an HII region, while IGR J18539+0727 and J21247+5058 are radio galaxies. They also report that the radio emission possibly associated with IGR J15479-4529 is extended suggesting an extragalactic emission. -IGR J06074+2205 and J18027-1455 are probably AGNs, while J17091-3624 is a possible microquasar. More details can be found in Pandey et al. 2005 accepted in A&A astro-ph 0509645 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #102 September 22th 2005 | Bird et al. 2005 (accepted for publication in ApJ) present the second IBIS catalogues. Among the 209 hard X-ray sources reported in this, Bird et al. identify 23 new IGR sources for which they give the hard X-ray position and fluxes. These are IGR J07506-1547, J07565-4139, J09026-4812, J11114-6723, J13020-6359, 14492-5535*, J15359-5720, J16194-2810, J16377-6423, J16482-3026, J16500-3307, J17088-4008, J17204-3554, J17445-2747, J17513-2011, J18048-1455, J18193-2542, J18214-1318, J18256-1035, J18259-0706, J19284+0107, J19308+0530, J21335+5105 * This source may be identical to J14493-5534 identified by Revnivstsev et al. 2005 See the catalogue or my web pages for the source positions and errors. They even propose tentative identification for some of them. J16377-6423 may be a cluster of galaxies J17088-4008 is an AXP (identification with RX J170849.0-400910?) J17204-3554 may be a molecular cloud (NGC 6334) J21335+5105 is a CV More details can be found in Bird et al. 2005 accepted by ApJ (forthcoming paper section) hopefully soon on astro-ph Stephen et al. 2005 used the Rosat catalogues to find for couterparts to new IGR sources from this 2nd IBIS catalogue. -J16194-2810: is identified as 1 RXH J161933.0-280738, is associated with GSC6806.00016 (=USNO B1 0618-0432633, with B~13.6-14), and is bright in 2MASS with J=8.3, H=7.3, and K=7 -J16377-6423: the Rosat source is associated with the cluster of Galaxies triangulum australis, CIZA 1638.2-6420 at z=0.058 with L(rosat)= 1 e45 erg/s -J16482-3036: In the Rosat error box lies a NVSS source at ra=16h 48m 16.6s and dec=-30deg 35' 07.5" with a flux of 3.5 mJy at 20cm. The source has B=15.82, R=13.38, J=13.94 and K=12.18. It is a likely background AGN For the other sources no clear identification is reported More details in Stephen et al. 2005 accepted by A&A, http://arxiv.org/abs/astro-ph/0509620 astro-ph 0509620 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #101 September 20th 2005 | Filippova et al. 2005 present INTEGRAL spectra from 35 X-ray pulsars. Six of these are IGR sources whose principle spectral parameters from a cutoff power law are (c.f. Lutovinov et al., 2005, astro-ph/0411550): IGR J16320-4751: nH=1.8x1023 (fixed), Gamma=0.7+/-0.2, Efold=13+/-1 keV IGR J16358-4726: nH=4.0x1023, Gamma=0.7+/-0.5, Ecut=16+/-5 keV IGR J16393-4643 (=AX J163904-4642), nH=5.8x1023, Gamma=1.3+/-1.0, Ecut=11+/-1 keV IGR J16465-4507: nH=7.2x1023, Gamma=1.0+/-0.5, Ecut=30 keV (fixed) IGR J17252-3616 (=EXO 1722-363): nH<1024, power law with Gamma=3.5 IGR J18027-2016 (=SAX J1802.7-2017): Gamma fixed at 0.1, and Ecut~10 keV More results can be found in Filippova et al., 2005 (Astronomy Letters) astro-ph 0509525 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #100 September 9th 2005 | Burderi et al. 2005 present a RXTE timing analysis of IGR J00291+5934 while in outburst. The authors revise the spin frequency to 598.89213053(2) Hz and they confirm the spin up (< 8x10^-13 Hz/s, c.f. Falanga et al., 2005), which they use in different torque models to estimate a mass accretion rate of about 9x10^-9 solar masses per year. Other aspects of this work can be found in: http://arxiv.org/abs/astro-ph/0509224 astro-ph 0509224 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #99 September 7th 2005 | Lutovinov et al. 2005 in a recently accepted paper, Lutovinov et al. 2005 analysed Galactic plane (l between 325°- 50°) INTEGRAL observations focusing on an analysis of HMXB. In their sample the authors mention the presence of several INTEGRAL sources, namely IGR J16318-4848, IGR J16320-4751, IGR J16358-4726, IGR J16393-4643 (refered to as AX J163904-4642), IGR J16465-4507, IGR J16479-4514, IGR J17391-3021, IGR J18027-2016. For these sources they studied the presence of pulsations, and analysed (non-simultaneous) soft X-ray (with ASCA, RXTE, or XMM) and soft gamma-ray (ISGRI) spectra. As main results (concerning those sources), they 1) refine the position to IGR J16479-4514 to RA=16h 48m 07s dec=-45° 12' 21" +- 0.9' 2) confirm the pulsation at 5980s of IGR J16358-4726 with ISGRI (18-60 keV range) 3) report the discovery of pulsations at 228 +- 6s in IGR J16465-4507 suggesting the compact object in this system is a pulsar. 4) report 1-100 keV spectral analysis (for the first time) of IGR J16465-4507, leading to Nh~72e22 cm-2, Gamma~1.0, Ec~30 keV suggesting the system is an HMXB. All details (including spectral fits to the other sources), as well as a discussion on the distribution of HXMB in the Galaxy can be found in Lutovinov et al. 2005, accepted for publication in A&A, astro-ph 0411550 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #98 September 2nd 2005 | Sguera et al. 2005 report on INTEGRAL detections of outbursts from three fast X-ray transients, among these: IGR J16479-4514, and IGR J17391-3021/XTE J1739-302. Their results confirm the very fast transient nature of the sources with outbursts lasting less than ~3 hours. Unlike other known fast X-ray transients, these sources were seen in outburst more than once in the last 2 years of ISGRI observations, which suggests a recurrent fast transient behavior. The 4 outbursts from IGR J16479-4514 are significantly shorter than expected of HMXBs or Be/NS systems. A flare lasting ~30 mins. with a peak flux of 850 mCrabs (1.3x1037 ergs/s assuming it is in the Norma Arm region) was found in the 20-30 keV light curve of one of these bursts. The authors discuss the timing properties of the source and say that it may be indicative of a Type I X-ray burst, therefore suggesting that the source is a neutron star in a LMXB. IGR J17391-3021 has an improved position (RA=17 39 08.52; Dec.=-30 19 55.8; 1.3' error) which places it 57" away from the Chandra position for XTE J1739-302, and significantly raises the chances that the sources are the same. The source spectrum is typical of a NS binary, most likely a HMXB given that its counterpart was identified as a blue supergiant, but its outbursts (lasting between 30 mins. and 3 hours) are shorter than expected for HMXBS or Be/NS binaries. More information on these sources can be found in Sguera et al. (2005, A&A in press) or at: astro-ph 0509018 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #97 September 1st 2005 | Falanga et al. 2005 (astro-ph 0508613) report on simultaneous INTEGRAL and RXTE observations of the accreting ms pulsar IGR J00291+5934. The average spectrum of the source is indicative of thermal Comptonisation with a electron temperature kT~50 keV, and Tau~1. The authors further say that the spectral shape remains almost constant over the outburst. The timing analysis presented in Falanga et al. allows the authors to detect the pulsation at high energy with ISGRI, up to 150 keV. They show that the pulse fraction increases with the energy from 6% @ 6 keV up to 12-20% at 100 keV. They also report the presence of soft lag whose energy dependence is rather complex. Falanga et al. discuss their results, show that the spectral parameters of IGR J00291+5934 are close and in agreement with those found in other MSPs. The energy dependence of the pulse fraction is also what expected by a Doopler boosting on the thermal comptonisation spectrum from the hot spot. More details can be found in Falanga et al. 2005 astro-ph 0508613 Kennea et al. 2005 report on the detection of flaring activity from IGR J16479-4514 with the Swift telescope. Using the XRT they refine the position to RA=16h 48m 07.0s Dec=-45° 12' 05.8" with an uncertainty of 6" During their observation the authors report the presence of 2 long flares the first one seen with the BAT while both were detected with XRT. The spectrum of the source is well fitted by an absorbed power-law, with N_H = 6.4 +- 0.9 x 1022 cm^-2 and Gamma=1.09 +- 0.25. The 0.5-10 keV mean flux is 3.8 e-11 erg/s/cm2. The UVOT detects a faint source compatible with the XRT position at RA= 16h 48m 06.8 Dec=-45° 12' 08.0" It is visible only in the V-band with Mv=20.4 +- 0.4 More details can be found in Kennea et al. 2005 Atel 599 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #96 August 29th 2005 | IGR J17464-3213 Rupen et al. 2005 report reappearance of this BHC in the radio domain using the VLA. They report a flux density at 4.86 GHz of 0.59 +- 0.07 mJy. More details in Atel 575 Soon after Swank et al. 2005 report that the source was active again in the X-rays since it was detected by the AMS onboard RXTE at a flux of 21mCrab on Aug 7. Further observations showed it was detected by the PCA, and that on Aug 11 the ASM flux was 63 mCrab. More details in Atel 576 Baylin et al. 2005, however, say that observing the source in optical, they see no increase in K nor in I. Atel 577 Kretschmar et al. 2005 report that IGR J17464-3213 had further brightened during INTEGRAL observations of the field. The averaged 5-200 keV spectrum is well fitted by a single powerlaw with Gamma=2.58+-0.08. Fluxes are 136+4-9 mCrab (5-20 keV) and 66+2-4 mCrab (20-100 keV). Atel 593 IGR J12349-6434 Tueller et al. 2005 report on the detection of IGR J12349-6434 (SWIFT J1234.7-6433) by SWIFT XRT. Only one source is found in the BAT error box, The XRT position id R.A.=12h34m54.7s , Decl.=-64d33m55.6s (+- 6" @ 90%) Therefore 5" from the symbiotic star RT Cru, confirming the suggested identification proposed in ATel # 528. Atel 591 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail #95 August 11th 2005 |
Paizis et al
(accepted in A&A) report on the
result of Chandra and RXTE observations of the accreting ms
pulsar IGR J00291+5934.
From their spectral analysis Paizis et al. show that the spectra of IGR J00291+5934
can be fitted with a two component model involving a thermal component and a
power law. While along the outburst the power law component show no particular trend
the thermal one (interpreted as a hot spot on the surface of the pulsar) becomes weaker
until it is not detected any more.
When analysing the simultaneous Chandra/RXTE observations, the 1~keV hot spot has
disappeared while a 0.4 keV thermal component shows up in the spectra.
According to the author this feature is the manifestation of the accretion disc.
These authors also report the possible presence of the 6.4 keV iron line with an
excess around 6.8 keV and an absorption feature around 7.1 keV. This is the first
observation of the two latter in a ms pulsar.
Paizis et al. further discuss the possible origin of those features and suggest
that they may originate in an expanding hot corona, with high outflow velocities.
More details can be found in Paizis et al. 2005
to appear tomorrow in astro-ph, theoreticaly under the number 0508258
astro-ph/0508258
| Mail #94 August 11th 2005 |
in't Zand 2005
(accepted in A&A Letters)
report on a 20 ks Chandra observation of the INTEGRAL
source IGR J17544-2619.
The use of Chandra allowed him to refine and improve the position
of the source to
RA=17h 54m 25.284s
Dec=-26d 19' 52.62"
with a nominal 90% uncertainty of 0.6".
With this improved position in't Zand confirms the association of
IGR J17544-2619 with 2MASS J17542527-2619526 which is identified as
a blue supergiant (this will be delt with in a forthcoming paper) located
at 3-4 kpc.
The source was first in quiescence and underwent a flare during the
observation.
The quiescent spectrum is very soft and suggest the compact object in
this source is a neutron star rather than a black hole.
The spectrum hardens significantly during the flare, while the
absorption column density shows no variations and remains at a
level compatible with the GAlactic absorption.
The author speculates on the origin of the flare, and suggets
that it must be related to the donor star, rather than the compact
object.
More details can be found in in't Zand 2005,
astro-ph 0508240
| Mail #93 August 8th 2005 |
Revnivtsev et al. 2005
report on
the results of a deep INTEGRAL exposure of the Crux Arm.
They publish a catalogue of sources detected with IBIS/ISGRI down
to a sensitivity of ~0.8-1mCrab. Besides a certain number of sources,
(and 5 known IGR sources) these authors report the discovery of 15 new
INTEGRAL sources. For some of them they even unveiled their nature.
These are: IGR J08023-6954,
RA=08h 02m 16.8s,
DEC=-69° 54' 36",
IGR J10109-5746,
RA=10h 10m 50.4s,
DEC=-57° 46' 48",
IGR J10252-6829,
RA=10h 25m 12.0s,
DEC=-68° 27' 36",
IGR J11085-5100,
RA=11h 08m 33.6s,
DEC=-51° 00' 36",
IGR J12026-5349 -> AGN, WKK 0560,
RA=12h 02m 40.8s,
DEC=-53° 49' 48",
IGR J12415-5750 -> AGN, WKK 1263,
RA=12h 41m 24.0s,
DEC=-57° 50' 24",
IGR J13109-5552,
RA=13h 10m 45.6s,
DEC=-55° 51' 36",
IGR J14175-4641,
RA=14h 17m 12.0s,
DEC=-46° 40' 48",
IGR J14471-6319,
RA=14h 47m 07.2s,
DEC=-63° 19' 48",
IGR J14493-5534,
RA=14h 49m 09.6s,
DEC=-55° 36' 00",
IGR J14552-5133 -> AGN, WKK 4488,
RA=14h 55m 14.4s,
DEC=-51° 33' 00",
IGR J14579-4308 -> AGN, IC 4518,
RA=14h 57m 45.6s,
DEC=-43° 08' 24",
IGR J15094-6649,
RA=15h 09m 18.8s,
DEC=-66° 51' 00",
IGR J15360-5750,
RA=15h 36m 00.0s,
DEC=-57° 50' 24",
IGR J16185-5928 -> AGN, WKK 6471,
RA=16h 18m 31.2s,
DEC=-59° 28' 12",
With an accuracy down to 6' for the weakest source (IGR J12415-5750)
All details in Revnivtsev et al. 2005
astro-ph0508155
In addition, some days ago, J. Halpern , reported Chandra and
optical identification of one of theses sources.
IGR J12026-5349 is located at RA=12 02 47.62, dec=-53 50 07.6
(typical Chandra error is 0.6")
For 2 other sources (IGR J10252-6829, and J11085-5100) only upper limit on the
Chandra rates are reported.
More details in Halpern
Atel 572
astro-ph 0508128
| Mail #92 August 5th 2005 |
Bélanger et al. 2005
report a deep analysis
of the Galactic Center field with INTEGRAL and some
contemporaneous XMM observations of a smaller field centered on
IGR J17456-2901.
Concerning IGR J17456-2901 the principal source of interest of this study,
the authors refine its position to
RA=17h 45m 42.5s
dec=-28° 59' 28"
with an uncertainty of 1 arcmin.
This position is compatible with that of Sgr A* which
confirms the result of Belanger et al. 2004 on the association
of IGR J17456-2901 and Sgr A*.
On the other hand, and contrary to what they had previously
suggested, IGR J17456-2901 show no particular variability on
time scales ks, day, week and month.
The broad band XMM/INTEGRAL 1-400 keV spectrum of this source is
well fitted with a model involving a two temperature plasma (kT~1 keV
and kT~6.5 keV), a Gaussian a 6.4 keV and either a cut-off power law
with Gamma~1 and cut-off energy 25 keV, or a broken power law
with Gamma1~1.5 and Gamma2~3.2, and break=27 keV.
Belanger et al. discuss several scenari explaining the (hard X-ray)
emission from IGR J17456-2901.
They in particular conclude that the hard X-ray emission cannot be
the extrapolation of the hot thermal plasma at 8 keV, nor can it be associated
with the integrated flux of the several known X-ray transients in the field.
This emission can neither be due to the extrapolation of flares from Sgr A*.
Further arguments lead them to suggest that IGR J17456-2901 is not a point like
source, but still is a very compact region of diffuse emission where both thermal
and non-thermal physical processes occur.
More detail can be found in Belanger et al. 2005 (accepted for publication
in ApJ),
astro-ph 0508128
| Mail #91 July 21st 2005 |
Ubertini et al. 2005
report the discovery of a new source IGR J18135-1751
with IBIS/ISGRI at a position coincident with that of the VHE source
HESS J1813-178.
The source is located at
ra = 18h 13m 27.2s
dec= -17° 50' 56"
with a nominal uncertainty of about 2' (90% confidence).
The authors discuss the possible assiociation of the HESS and
INTEGRAL sources and suggest that both are the same source.
They also search for counterparts at other wavelength, and found
a possible X-ray counterpart AGPS 273.4-17.8 in the ASCA archival
data.
The source is persistent and has a 20-100 keV luminosity of
5.7e34 erg/s (if located at 4 kpc). While the X-ray spectrum
is well fitted by an absorbed power law with photon index 1.8 and
N_H~5 e 22 cm-2
At other wavelength no Optical nor IR (candidate) counterparts are
found, but some candidate radio counterparts are reported.
The authors discuss the possible type of source IGR J18135-1751 is
and favour a Pulsar Wind Nebula embedded in a SNR.
More details in Ubertini et al. 2005 accepted in ApJ Letters
astro-ph 0505191
| Mail #90 July 4th 2005 |
Krivonos et al. 2005
report the discovery of a new
transient IGR J11321-5311, with the ISGRI detector
onboard INTEGRAL during deep observations of the Crux
spiral arm.
The position is
RA=11h 32.1min
dec=-53°11'
with a nominal uncertainty of 2'.
The authors report that the source spectrum is hard
which, according to them, suggests the source is a black
hole binary.
It remained active for about3 hours before decreasing below
3 mCrab.
More details in Krivonos et al. 2005 Atel 545
Atel 545
| Mail #89 June 29th 2005 |
Bassani et al. 2005
reporting preliminary results from the
forthcoming 2nd IBIS/ISGRI catalogue, mention that
2 previsoulsy unknown sources, IGR J10404-4625 & IGR J16482-3036
may be AGNs.
The Gamma-ray coordinates of the sources are
-IGR J10404-4625:
RA= 10h 40m 22s
Dec=-46° 24' 58"
-IGR J16482-3036:
RA= 16h 48m 09s
Dec=-30° 35' 35"
(the errors are not given, 2-3' ?)
Both sources have a radio counterpart
SUMSS J104022-462525 at RA=10h 40m 22.23s, dec=-46° 25' 25.6"
for IGR J10404-4625, and NVSS J164816-303507 at RA=16h 48m 16.60s,
dec=-30° 35' 07.5" for IGR J16482-3036.
Those two sources have also 2 MASS extended infrared counterparts which suggest
they are AGN.
In addition according to Bassani et al., IGR J10404-4625 is an emission line galaxy
with a redshift z=0.0239.
More details in Bassani et al. 2005
Atel 537
| Mails #87 &
#88: June 22th 2005 |
Revnivtsev et al. 2005
report that the x-ray pulsar IGR J11435-6109
has apparently entered in outburst.
These authors observe that the source flux has gradually increased
from below 0.5 mCrab to ~15 mCrab in about 10-18 days.
More details in Revnivtsev et al. 2005
Atel 531
Masetti et al. 2005
report on the possible association of
the emission-line symbiotic star RT Cru with the newly
discovered INTEGRAL source IGR J12349-6434.
The authors remark that this source is the only SIMBAD
object within the INTEGRAL error box.
This possible association is reinforced by the fact that
RT Cru shows large-amplitude (Dm ~3.8 mag) outbursts and
short-term flickering, both behaviour typical of accreting
binary systems
More details in Masetti et al. 2005
Atel 528
| Mail#86: June 19th 2005 |
Juett et al. 2005
report on the results of observations of
the field containing IGR J17473-2721 with Chandra/HRC.
They found a single source in the 30'x30' images at a position
RA = 17 47 18.06
Dec. = -27 20 38.9
(error 0.8" at 90%)
From comparison with the Swift detection and the RXTE detection
of a source in this area, the authors conclude that
IGR J17473-2721 and XTE J1747-274 are the same.
These authors also performed an observation with the 6.5-m
Magellan I, and the PANIC camera.
One infrared (Ks=16.2 mag) source was found in the Chandra error circle
with a position of
RA = 17:47:18.08
Dec. = -27:20:38.7,
0.3" from the X-ray position.
Juett et al. fruther argue that all the properties of these source show that
it does not belong the the class of obscured HMXB.
PANICS Ks image avalaible at
http://www.astro.virginia.edu/~amj3r/XTEJ1747/XTEJ1747-274_panic_Ks.jpg
More details in Juett et al. 2005
Atel 521
| Mail#85: June 17th 2005 |
Chernyakova et al. 2005
report the discovery of a new source
IGR J12349-6434 with the ISGRI detector onboard the INTEGRAL
observatory.
The source is located at
ra=12h 34m 54s
dec=-64° 34' 06"
(+-2' 90% confidence)
The source was detected inmosaic images accumulated from 3 different epochs
between January 11 2003 and March 22 2004, at fluxes ~3.5 mCrab.
The average flux in 16 - 20 keV, 20 - 30, 30 - 40, 40 - 60, 60 - 100 keV
was equal to 5.3+/-0.1 mCrab, 4.3+/-0.4 mCrab, 3.3+/-0.5 mCrab, 2.7+/-0.5 mCrab,
and 1.6+/-0.8 mCrab respectively.
More details in Chernyakova et al. 2005
Atel 519
| Mail#84: June 8th 2005 |
Beckmann et al. 2005 (accepted in ApJ)
report on the results of
observations of the Norma arm INTEGRAL source IGR J16283-4838 with
Swift, INTEGRAL, RXTE and Spitzer.
The high energy observations reveal the source is higlhy absorbed,
with a variable absorption column density, Nh, comprised between
0.4 and 1.7 e22 cm-2. The spectrum as seen with Swift/XRT and
RXTE/PCA is well fitted with a powerlaw with a photon index ~1.
The authors also report that an absorbed blackbody represents the data
well. In this case the BB temperature is ~2keV.
No Fe line is detected with a 3sigma upper limit of 3e-4 ph/cm2 at
6.4 keV (line EW <600 eV).
The authors discuss the possible type of the source and by comparison
with other IGR sources and well known HMXB suggest that IGR J16283-4838
is a new member of highly absorbed HMXB, probably with a neutron star
as primary although a black hole can not be ruled out (in particular no
coherent pulsations are found in the PCA data).
More details can be found in Beckmann et al. 2005
astro-ph 0506170
| Mail#83: May 25th 2005 |
Kennea et al. 2005 report on a Swift observation of the field of
XTE J1747-274, these authors find a bright source at coordinates
RA= 17h 47m 17.8s
DEC= -27° 20' 39"
with an uncertainty of 6" (@ the 90% confidence level)
This is 66" away from the transient IGR J17473-2721
and 7' from the RXTE position. The fact that no other sources are detected
by Swift/XRT lead Kennea and co workers to conclude that this bright source is
IGR J17473-2721.
The spectrum they extracted could be fitted by an absorbed power law with
Nh=(5.2 +- 0.4) e22 cm-2, and Gamma=2.12 +- 0.16 leading 0.5-10 keV flux
of 8.4e-10 erg/s/cm2.
More details can be found in Kennea et al. 2005
Atel 500
| Mail#82: May 20th 2005 |
Barlow et al. 2005 (Accepted in A&A)
report on the results of
observations of IGR J17285-2922 with INTEGRAL.
The authors reanalysing large sets of data first show that the
source is a transient, and they refine the gamma-ray position to
ra=17h 28m 41s
dec=-29° 22' 56"
(uncertainty of 2')
According to the monitoring of IGR J17285-2922 by INTEGRAL
the source entered an outburst on IJD 1365 (MJD 52909 or Sept
27 2003), which terminated before IJD 1503 (MJD 53047 or feb 12 2004)
when the source was next visible with INTEGRAL.
The spectrum the authors could extract is well fitted with
a powerlaw of photon index 2.1, and IGR J17285-2922 has a
20-150 keV flux (averaged over 191 ks) of 1.1 e-10 erg/s/cm2.
Barlow et al. 2005 discuss these observational facts and propose
that IGR J17285-2922 is a Galactic X-ray binary.
The nature of the compact object (BH or NS) and that of the system
(HMXB or LMXB) are discussed although no conclusions can be
drawn from the data presented.
More details can be found in Barlow et al. 2005
Astro-ph 0505405
| Mail#81: May 17th 2005 |
Steeghs et al. 2005 (Atel 494) report on further investigation of their Magellan I band
images of the field of IGR J17098-3628 (see Atel 478).
The authors identify a point source at
R.A.=17:09:45.93,
DEC= -36:27:58.2
(0.2" error) which is within the 2 sigma error box of the radio counterpart
recently reported by Rupen et al. (Atel 490).
Steeghs et al. also obtained additional I band images, that showed that this point
source had faded by ~0.12 mag.
The positional coincidence and variability makes this source the very likely
optical counterpart to IGR J17098-3628.
More details in Steeghs et al. 2005
Atel 494
Reig et al. 2005 (accepted in AA) report on results of their search for optical counterpart
to HMXB sources. This work concerns in particular two IGR sources namely IGR J01363+6610
and IGR J00370+6122 for which the authors respectively identify the optical counterpart and
publish the first detailed optical spectrum.
- For IGR J01363+6610, the proposed optical counterpart is that already reported by Reig et al. 2004
(Atel 343). The spectrum shows the presence of H beta and gamma emission line
and the metallic and HeI lines, which are typical of and eerly B type star.
More detailed sepctroscopic analysis suggests the star os a main sequence B1V star.
From magnitudes considerations the authors locate the source at ~2kpc from the Sun.
B~14.68, V~13.29, R~12.32, I~11.37, (although with slight variations as can be seen in
their Table 1).
- For IGR J00370+6122 the authors suggest that the proposed optical counterpart
BD +60°73 (=LS I+61°161) by Den Hartog et al. 2004 (Atel 281), Rutledge 2004 (Atel 282)
is an evolved B0.5 II-III star.
The authors discuss their findingsd and say that unless this source has an eccentric orbit the
production of X-ray in this system is difficult to understand.
More details can be found in Reig et al. 2005
Astro-ph 0505319
| Mail#80: May 13th 2005 |
Rupen et al. 2005 (Atel 490)
report on the results of VLA (4.86 GHz) observations
of the field around IGR J17098-3628 made on March 31st, April 5th, 12th an May 4th.
They detect a unique radio source within the INTEGRAL error box of 2 arcmin at a position:
RA=17h 09m 45.934s +- 0.011s
DEC=-36d 27' 57.30" +- 0.55"
This position is at 0.8 arcsec from the Swift-XRT position, and therefore well within the
5" Swift error box.
This position is, however, inconsistent with the positon of the counterparts suggested by Kong
2005, Blustin et al. 2005.
The radio history of the source is consistent with its X-ray evolution, and the good agreement
between the VLA source and the Swift position suggest this radio source is the genuine
counterpart to IGR J17098-3628.
More details can be found in Rupen et al. 2005
Atel 490
Images of the observations can be found at
http://www.aoc.nrao.edu/~mrupen/XRT/I1709BB/i1709bb.shtml
(Courtesy M. Rupen)
| Mail#79: May 12th 2005 |
Joinet et al. 2005 (accepted in ApJ)
report on monitoring of
the 2003 outburst of IGR J17464-3213/H1743-322 with INTEGRAL and
RXTE, and they particularly focus on analysis of the data obtained
with the INTEGRAL/SPI and RXTE/PCA detectors during March 21-April
22 2003.
They describe the spectral evolution of the source along the outburst.
The latter started with an initial hard state, and the source gradually
softened through an intermedate state until Apr. 8 when a radio outburst
occured. During this period the author reports that the gradual softening
of the source is characterized by a shift of the pek of the SED from about
100 keV down to 10 keV on Apr. 8.
After that the source was in a steep power law state characterized by strong
flaring activity. The X-ray spectral shape seems to be unafected by the flaring
activity.
The authors discuss those findings in the framework of various models
of outbursts and state transitions of black hole transients, and show that
the radio flare is apparently not associated with the peak of the
soft/hard X-ray outburst.
More details can be found in Joinet et al. 2005 (to be published in)
ApJ, preprint available at:
http://www.journals.uchicago.edu/ApJ/journal/preprints/ApJ61781.preprint.ps (need subscription to ApJ) | Mail#78: May 9th 2005 |
- IGR J18027-2016: Hill et al. 2005 (accepted in A&A) report on the results of
observations performed with INTEGRAL, XMM, (and Beppo-SAX).
They confirm the association of the hard X-ray source with SAX J18027-2016,
giving a refined and more accurate position of the source at
RA = 18h 02m 46.1s
Dec= -20deg 17' 37.1"
with an uncertainty of 1'
using a 30.5 sigma detection in a 20-40 keV mosaic from INTEGRAL/ISGRI.
Using the same detector and the long monitoring time (417 days) the author
also confirm the eclispsing nature of the source and report an orbital period
of the system of 4.57 days (compatible to what was found with Beppo-SAX, although
with a high uncertainty).
From XMM-PN the author detect a pulse in the X-ray light curve of the source at 139.47s
consistent with previous measurments.
The spectral analysis of XMM and INTEGRAL is fitted by a model consisting of
an absorbed broken powerlaw with a Gaussian line. The authors report the
presence of a soft excess below 3 keV that they fit with a borad Gaussian.
They measure Nh~7e22 cm-2 which is then likely intrinsic to the system.
Hill et al. discuss all their findings, and besides other conclusions, give a mass
function of the system of 16+-1 Msol, propose that
IGR/SAX J18027-2016 is a High Mass X-ray binary consisting of pulsar orbiting a
~18.8-29.3 Msol OB star.
More details can be found in Hill et al. 2005
astro-ph 0505078
- IGR J00291+5934: Jonker et al. 2005 (accepted in MNRAS) report on the results of 3 Chandra observations of
this millisecond X-ray pulsar, at the end of its 2004 outburst. In addition to that they
also report a detection of this source in quiescence with ROSAT in 1992.
From the comparison of the Chandra observations with the ROSAT one, the authors say that
the source had already reached quiescence during their observations.
They first fitted their spectra with a simple (absorbed) blackbody. Even we leaving
Nh as a free parameter the authors remark that the temperature of the BB is high (~0.3 keV)
when compared to other NS X-ray transients. Alternatively, adding a power law with
a fixed photon index brings the temprature down to a slightly lower value (~0.28 keV).
Jonker et al. studying the X-ray light curves during these quiescent observations show that
even in this state variability occurs. This is the first time that this is seen in
a millisecond X-ray pulsar, while it had already been reported in the case of other
NS transients.
More details can be found in Jonker et al. 2005,
astro-ph 0505120
| Mail#77: May 4th 2005 |
Steeghs et al. Atel
478 report on the results of Optical and NIR imaging
of the field of 2 IGR sources obtained with the 6.5m Magellan-Baade telescope:
- IGR J17098-3628: The authors report that the possible counterpart proposed by Kong in Atel 477
is actually a blend of several sources as they can see in a I band image obtained with
the imaging spectrograph IMACS. Comparison of the SuperCOSMOS sky survey image and the
360s IMACS image is available at: http://hea-www.cfa.harvard.edu/~dsteeghs/IGRJ17098-3628.jpg
- IGR J16283-4838: the authors obtained K band images with a different camera named PANIC.
They also fnd here several point sources within the Swift error box of the source,
and remark also that the counterpart candidate proposed by Rodriguez and Paizis (Atel 460)
is also a blend of point sources.
Steeghs et al. say, however, that preliminary relative photometry yields K~14.1 for the brightest
source resolved in their image consistent with the K~14 reported by us in Atel 460.
A comparison between the 2MASS field and their 300s PANIC K-band image is available at:
http://hea-www.cfa.harvard.edu/~dsteeghs/IGRJ16283-4838.jpg
More details can be found in Steeghs et al. 2005
Atel 478
Concerning IGR J17098-3628, Blustin et al. Atel 479 further report a possible
identification of the optical counterpart to this source with the UV/Optical Telescope
on board Swift (UVOT). These authors detect a V=19.3 +- 0.1 star at at R.A.=17h09m46.161s,
Decl.=-36d27m58.05s, apparently identical to the SuperCOSMOS candidate.
An image of the Swift-UVOT source is available at
http://www.mssl.ucl.ac.uk/twiki/bin/view/SwiftBA/IGRJ17098-3628 .
More details can be found in Blustin et al. 2005
Atel 479
| Mail#76: May 3rd 2005 |
Kennea et al. Atel
476 report on the preliminary analysis
of a 2.8 ks observation of IGR J17098-3626 with Swift XRT.
The authors refine and improve the position
to the source to
RA=17h 09m 45.9s
Dec=-36deg 27' 57"
with an estimated uncertainty of 5" arcsec.
On May 1st, at the date of the observatiuon, the source was bright
with an average flux of 1.3e-9 erg/s/cm-2, with Nh of the order of
1e22 cm-2.
A possible fading during the observation is also mentioned.
More details in Kennea et al. 2005
Atel 476
Further to the improvement of the X-ray position,
Kong 2005 Atel 477 report the identifictaion of a possible
Infra red counterpart to IGR J17098-3626 from the 2MASS
catalogue, and a possible optical counterpart from the
SuperCOSMOS Sky Survey.
- The IR counterpart (2MASS J17094612-3627573),
has magnitudes J=14.69, H=13.66, and
K=13.37, and lies about 2.7" from the X-ray position.
- The optical counterpart is at R.A.=17h 9m 46.166s
and Dec.=-36d 27m 57.50s, (@ 3.25" from the Swift
position), and has magnitudes B=21.16, R=19.43, and I=18.75.
More details can be found in Kong 2005
Atel 477
| Mail#75: Apr. 29th 2005 |
In a review paper
E. Kuulkers reports the main properties of the "IGR sources" which have been
found to have a rather high absorption column density (>~ 1023 cm-2).
Besides summarising all those properties, E Kuulkers mention that the
location of the source in the Galaxy suggests that the companion star (donor) is
probably a giant or supergiant star.
The sources discussed in this review include IGR J16195-4945, J16318-4848, J16320-4751,
J16358-4726, J16393-4643, J16418-4532, J16493-4348, J16465-4507 and J16479-4514 from the
Norma arm region, and IGR JK19140+0951 from the Sagitarius arm
More details in Kuulkers 2005, "An absorbed view of a new class of INTEGRAL sources"
in Interacting Binaries: Accretion, Evolution and Outcomes
astro-ph 0504625
| Mail#74: Apr. 25th 2005 |
Two new sources and related informations about them:
IGR J17473-2721 :
Grebenev, Molkov and Sunyaev 2005 report on the discovery of a new source
IGR J17473-2721, with the ISGRI detector onboard INTEGRAL.
The source is located at
R.A.=17h47m21s,
Decl.=-27d21m29s
(equinox 2000.0, uncertainty 2')
While the first detection is reprorted from an umtra deep mosaic image,
the author report that it is also detected on smaller time scale of ~a
revolution (3 days), with an apparent increase in the X-ray flux
More details can be found in Grebenev et al. 2005
Atel 467
*IGR J11215-5952* :
- Lubinski et al. report on the discovery of another new hard X-ray source
with ISGRI, labeled IGR J11215-5952.
The source is located at :
RA=11h21m45s,
DEC=-59d52'
(+- 3')
The source was detected in 2 pointings (~2100s each) only in the 20-60 keV
energy range. The non-detection at higher energy suggests a soft spectrum.
More details can be found ion Lubinski et al. 2005
ATel 469
- Concerning the same source
Negueruela, Smith and Chaty 2005, note that the B supergiant HD 306414
lies only 16" away from IGR J11215-5952.
However the author report also the presence of 3 other fainter sources in the
INTEGRAL error box.
The author disccus the possible asssociation of the optical counterpart with
the X ray source, and suggest that by comparison with other INTEGRAL sources
HD 306414 is the best candidate counterpart.
More details in Neguerela et al. 2005
Atel 470
| Mail#73: |
Markwardt, Swank & Smith 2005 report on some RXTE observations of 2 recently
discovered INTEGRAL sources, IGR J16283-4838 and IGR J16493-4348.
IGR J16493-4348: Although significant contamination by the Galactic ridge, the authors
managed to obtain a spectrum of the source. The latter is well fitted by an absorbed
power law, with Nh~1e23 cm-2 and Gamma=1.4. No line is required in the fits.
The 2-10, 10-20 and 20-40 keV bands are 1.0, 1.3 and 2.1 (units of 1 e-11
erg cm-2 s-1). The authors do not detect any period in the X-ray, even at the
known pulse period of PSR J1649-4348, which has been suggested to be associated to
IGR J16493-4348.
IGR J16283-4838: As in the previous case significant Galactic contamination is
observed in the RXTE X-ray spectrum of the source. The background corrected
spectrum is well modeled by an absorbed power law with Nh~4-5 e2 cm-2 and Gamma~0.8-1.1
While increase in the X-ray fluxes had been previously reported, the RXTE observations
showed decrease in the 3 energy ranges (2-10, 10-20 and 20-40 keV)?
The authors do not detect any pulsations.
More details in Markwardt et al. 2005
Atel 465
| Mail#72: |
Gænsicke et al. 2005 report on the identification of IGR J17303-0601
(1RXS J173021.5-055933) as an intermediate polar.
Through optical photometry of the optical counterpart they identifiy a spin period for
the white dwarf of 120s (which is the second-shortest spin period discovered so far).
From time resolved spectroscopy the auhtors report a possible orbital period of
925.27min. These authors discuss briefly those findings in the context of evolutionary
state of those systems.
More details can be found in Gænsicke et al. 2005
Atel 463
| Mail#71: |
Thanks to the improvement of the X-ray position of IGR J16283-4838,
by Kennea et al. 2005, Rodriguez & Paizis report the identification
of a possible infrared counterpart to the source in analysis of the 2MASS
archive images.
A clear source is detected in the K band at a position :
R.A.= 16h 28m 10.83s, Decl. =-48deg 38' 56.1" (+-0.11" at 90%)
which is about 1.1 " from the position returned from SWIFT-XRT.
Magnitude estimates are Ks = 13.95 +- 0.058, J > 16.8 , H > 15.8
(95% lower limits) and the source is not detected in DSS-2 plates
in either the red or the infra-red image.
The combined 2-MASS J H K image can be found
here
More details in Rodriguez and Paizis 2005
Atel 460
| Mail#70: |
Kennea et al. 2005 report the preliminary results of a ToO with the Swift
satellite on the newly discovered source IGR J16283-4838.
The analysis of the XRT aboard SWIFT allowed the authors to refine the position of
the source to ra=16h 28m 10.7s, Dec=-48d 38' 55" with 5" arcsec uncertainty at 90% confidence.
The authors also report that the source is highly absorbed with no detected X-ray emission
below 1.5 keV.
More details can be found in Kennea et al. 2005
Atel 459
| Mail#69: |
further to the discovery of IGR J16283-4838 by Soldi et al. Atel 456,
Paizis et al. report on follow up observations of this new source during an
open time ToO on the microquasar GRO J1655-40.
These authors note that the flux from the source has ~ doubled since the discovery
and now reaches a level of 8.5 mCrab in the 20-60 keV energy band.
More details in Paizis et al. 2005
Atel 458
| Mail#68: |
Soldi et al. 2005 report the discovery of a new source IGR J16283-4838 with the ISGRI
detector onboard the INTEGRAL observatory, in a (126 ks) mosaic image of an
observation of the Norma region of the Galaxy. It has a 20-40 keV flux of 3.6 mCrab,
while it is not detected at higher energy
IGR J16283-4838 is located at
ra=16h 28.3m
dec=-48deg 38'
(+-3 90% confidence)
More details in Soldi et al. 2005
Atel 456
Grebenev et al. 2005, report on the discovery of a new source IGR J16493-4348
with ISGRI. They suggest this hard X-ray source could be the counterpart to the
radio pulsar PSR J1649-4349 detected in 2004. The position obtained by Grbenev and
co-worker is
ra=16h 49m 21s
dec=-43deg 48m 36s
(+-2' @90%), which is 45 arcsec from the best position to the pulsar.
Based on some estimate of the pulsar activity, luminosity, the authors discuss the possibility
of either PSR J1649-4349/IGR J16493-4348 beeing the same source at the stage of transition to
LMXB, or that IGR is a genuine new source not associated to the pulsar.
More details in Grebenev et al. 2005,
Atel 547
| Mail#67: |
In the April 10th edition of ApJ, Homan et al. 2005 report on the study
of the variability of the BHC H1743-322 (also known as IGR J17464-3213
(XTE J1746-322, XTE J1746-319, H 1741-32) during the 2003-2004 outburst,
with RXTE.
These authors have observed this source in most of the (BH) spectral states
(which seems confirmed by the spectral analysis that have been submitted to ApJ),
although some obsevations seems difficult to classify.
The core of this paper is the identification and study of the varaibility and
the low and high frequency Quasi Periodic Oscillations (the latter
at frequencies 240 and 160 Hz).
Homan et al. further discuss the timing properties of H1743-322 and its QPOs
in the framework of theoretical models.
More details in Homan et al. 2005, ApJ 623, p. 383
| Mail#66: |
Mowlavi et al. 2005 report on some results concerning IGR J17098-3628 from
the monitoring of the Galactic bulge performed by Kuulkers and co-worker.
This field has been observed on March 26, April 2, and April 3.
The source had respective fluxes of ~50 mCrab (consistent with the report by Grebenev et
al. in Atel 447), ~12 mCrab and ~9 mcrab in the 20-60 keV range.
While a significant detection was achived on March 26 in the 60-150 keV range (~50 mCrab),,
only upper limits of ~15 mCrab can be deduced for the following observations.
The authors also reports that the source was never detected in previous
Galactic bulge monitoring observations.
More details in Mowlavi et al. 2005
Atel 453
| Mail#65: |
Grebenev et al. report on follow up observations of IGR J17098-3628 with both INTEGRAL and
RXTE.
The INTEGRAL/ISGRI spectrum can be well fitted by a power law without any evidence for
a cut-off up to 200 keV. The authors report a significant evolution of the source spectral
behaviour with a photon index of the power law evolving from 1.81 on March 24-25 to 2.10
on March 26. The
The light curves ad X-ray image of IGR J17098-3628 obtained with ISGRI are avalaible here:
http://hea.iki.rssi.ru/~sergei/igrj17098-3628.html.
RXTE also detected the sourc at a position consistent with that of INTEGRAL.
The spectrum consists of a superposition of a black body
component with kT~1.0 keV and a hard power law tail with Gamma ~2.5.
The hydrogen column density did not exceed 1022 cm^-2.
The X-ray behaviour of the source seems to indicate IGR J17098-3628 contains
a black hole, and that the system is therefore an X-ray nova
More details in Grebenev et al. 2005
Atel 447
| Mail#64: |
Grebenev et al. report the discovery of a new source IGR J1709.8-3628
with the ISGRI detector onboard the INTEGRAL observatory.
The source is located at
ra=17h 09.8m
dec=-36d 28'
(+-2 arcmin @ 90% confidence)
The source is detected at fluxes 28.2 mCrab in the 18-45 keV
and 38.7 mCrab in the 45-80 keV energy ranges.
More details in Grebenev et al. 2005
Atel 444
| Mail#63: |
Kuulkers and co-workers observe the Galactic
Bulge on a regular basis, performing each time an hexagonal pattern
(7 pointings). This allows a nice monitoring of the numerous X-ray sources
lying in this field.
Kuulkers et al. have decided to make the light curves of all these sources
publicly available through dedicated web pages.
Everything can be found under
http://isdc.unige.ch/Science/BULGE/
This monitoring concerns a certain number of so-called 'IGR sources'.
Through the afore mentioned web site source activity can be obtained for:
IGR J17091-3624, IGR J17200-3116, IGR J17252-3616, IGR J17254-3257
IGR J17285-2922; IGR J17331-2406, IGR J17391-3021, IGR J17407-2808
IGR J17456-2901, IGR J17460-3047, IGR J17464-3213, IGR J17475-2822
IGR J17488-3253; IGR J17507-2856, IGR J17544-2619, IGR J17597-2201
and IGR J18027-2016
| Mail#62: |
Neguerela et al. Atel 429 report on optical spectral analysis with the NTT of the only
star in the XMM-Newton error box of IGR J16465-4507 (USNO-B1.0 0448-00520455
= 2MASS J16463526-4507045).
The authors further suggest the association of this reddened early-type
supergiant with the Gamma-ray source.
The the object is estimated to be a B0.5I star.
The authors also suggest that IGR/XTE J17391-3021, IGR J17544-2619 and IGR J16465-4507
define a new class of transients characterized by very short outburst, and evolved
counterparts.
More details in Neguerela et al.
Atel 429
| Mail#61: |
Lutovinov et al. 2005, report on the discovery of
X-ray pulsations in archival ASCA and XMM observations of
IGR J16320-4751.
While two possible periods are found in the ASCA data (@ 1292 +-40
and 1510 +-50s) XMM confirms the presence of a strong
modulation at 1309 +- 40 s.
This modulations therefore favour a pulsar as the compact object
in IGR J16320-4751.
The pulse fraction, as deduced from the XMM observation, is ~26%.
More details can be found in Lutovinov et al. 2005 accepted for
publication as a letter in A&A.
The revised preprint should be available soon
on astro-ph :
astro-ph 0411457
| Mail#60: |
Galloway et al. 2005 report on RXTE observations of the
millisecond X-ray pulsar IGR J00291+5934.
These authors focus on the timing analysis of the source,
and show that the 599 Hz pulsation has a fractional amplitude
of 8% in the PCA 2-20 keV range.
Studying the energy dependence of the pulse, they find the the
pulse in the 6-9 keV X-rays arrives up to 85 microsecond
before that in the lower energy range.
At the same time the fractional amplitude of the pulsation is higher
at low energy.
From their analysis Galloway et al. also suggest the source lies at
(at least but not much further than) 4 kpc from us, although
they caution the reader with this estimate.
More details in Galloway et al. 2005, accepted
for publication in ApJ letters
astro-ph 0501064
| Mail#59: |
Stephen et al. (2005) report on their search for soft X-ray counterparts to
some of the INTEGRAL sources in the Rosat bright source catalogue.
For 8 of the "IGR sources" these authors propose the following association(s):
-> IGR J15479-4529: seems associated with 1RXS J154814.5-452845 an intermediate polar
cataclysmic variable.
-> IGR J16167-4957: 1RXS J161637.2-495847
-> IGR J16558-5203: RXH J165605.6-520339 (=1RXS J165605.6-520345??)
the ROSAT position allowed a possible infra red/optical
counterpart to be proposed. The source lies at
RA=16h 56m 05.6s
dec=-52deg 03' 40.4"
it is a possibly extended source with B~14.5 and R~13.5
-> IGR J17303-0601: 1H 1726-058, XSS17309-0552(?). This source is discussed in more
details in Masetti et al. 2004 (AA 426, L41)
-> IGR J17195-4100: 1RXS J171935.6-410054. Only one optical counterpart in the Rosat error
box with B~15, at a position ra=17h 19m 35.94s and dec=-41deg 00' 53.5"
A possibly extended or unresolved infra red source lies within 2.2" of the optical counterpart.
-> IGR J17200-3116: 1RXS J172006.1-311702. Here again only one optical counterpart lies in
the Rosat error box. It has B~19, and lies at RA=17h 20m 06.1s dec=-31deg 17' 02.0"
A possible infra red counterpart is also reported.
-> IGR J17254-3257: 1RXS J172525.5-325717. Only one optical counterpart lies in
the Rosat error box. It has B~18-19, and lies at RA=17h 25m 26.03s dec=-32deg 57' 06.1"
-> IGR J17488-3253: RXH J174854.9-325448 (=1RXS J174854.7-325444?)
No optical, radio or infra red counterpart is found in the few arcsec error box
at the position of the RXH source.
A possibly extended R~16 source is found at the edge of the Rosat error circle though.
All the possible optical and/or infrared counterparts need to be further confirmed.
All the details (including best position to the Rosat sources), can be found in
Stephen et al. 2005, accepted in AA letters
Preprint
| Mail#58: |
Bikmaev et al. (2005 Atel 395) report on optical monitoring of the transient optical
counterpart of IGR J00291+5934.
These authors observe a flux decay nearly exponential with an efolding time of
~5.7 days, therefore consistent with the decay rate of the X-ray flux.
Some optical brightness variations are also reported during time when the source is
bright enough, as well as a possible re-brigthening of this counterpart about 40 days
after the burst.
More details in Bikmaev et al.
Atel 395
| Mail#57: |
Shaw et al. report on INTEGRAL analysis of IGR J00291+5934 at the time
of its discovery (see Eckert et al. 2004, Atel 352)
From the only pointing where both a JEM-X and ISGRI spectrum can be obtained,
these authors fitted it with a simple phenomenological model consisting of an absorbed
powerlaw. The best fit parameters leads to Gamma=1.8 and a 5-50 keV flux of 8.3e-10
erg/cm2/s .
In order to try to constrain better the physics, they also constructed a high energy spectrum
using all ISGRI pointings. The best fit model is a model of thermal comptonisation with
an electron temperature of ~25 keV and an optical depth tau~3.6.
Shaw et al. also discuss the similarities of this system with the 5 other known ms X-ray
pulsars.
More details in Shaw et al. 2005 accepted for publication in A&A Letters
astro-ph 0501507
| Mail#56: |
den Hartog et al. (2005) report the discovery of a new source
IGR J00234+6141 with the ISGRI detector onboard the INTEGRAL observatory.
This source was detected during deep analysis of data of the Cassiopeia
region taken in december 2003 and February 2004.
The source is located at
ra=0h 23m 24s,
Decl. = +61o 41' 32"
(+-3' @ 90% confidence)
The authors also report a marginal detection with the ASM on board
RXTE. They also suggest that the source is a Galactic X-ray binary.
More details in den Hartog et al. (2005)
Atel 394
| Mail#55: |
Corbet & Remillard (2005) confirm the ~52.5 days
orbital period of IGR J11435-6109 (already proposed by in 't Zand & Heise 2004, ATEL #362)
using data from the All Sky Monitor aboard RXTE.
The best sine fit to the data gives a period of 52.46 +- 0.06 days.
More details in Corbet & Remillard (2005)
Atel 377
| 2004 |
Mail#54: |
We (Rodriguez et al. 2005) report on analysis of INTEGRAL and RXTE observations of the
high energy source IGR J19140+0951 (EXO 1912+097).
The iNTEGRAL coverage indicates that this source spends most of its time in a low
luminosity state, which likely corresponds to the state observed during the RXTE observations,
and is therefore characteristic of thermal comptonisation.
We observe in some occasion variations of the flux by a factor of ~10, during which the spectrum
can show evidence of a black body component.
The spectral parameters obtained from our spectral fits to the data, the observed variations
of Nh between the RXTE observations, the detection of an iron line, whose flux varies strongly
between the "states" suggests that IGR J19140+0951 is very similar to Vela X-1, GX 301-2, 4U 2206+54,
and is therefore probably a neutron star in a HMXB system.
More details in Rodriguez et al. (accepted for publication in A&A 2005),
astro-ph 0412555
| Mail#53: |
Torrejon & Negueruela 2004 report on optical observations of the field
of IGR J11435-6109.
Further to the possible association of the INTEGRAL source with 1RXS J114358.1-610736,
the authors first focus on the single star within the Rosat error box.
From their analysis they exclude 1RXS J114358.1-610736 to be the same source as
IGR J11435-6109.
Extending their study to the field around the authors found a moderately bright star
USNO-B1.0 0288-0337948 @
RA= 11h44m10.7s,
Dec= -61d07'02"
showing H alpha emission, and with B2=13.17, R2=12.95, I=11.61
Further analysis revealed this star is a Be (approximate type B3).
Torrejon & Negueruela further suggest that this source is the likely counterpart to
the INTEGRAL source, making IGR J11435-6109 a Be X-ray binary a possibility compatible
with its X-ray properties.
More details in Torrejon & Negueruela 2004 Atel 370
| Mail#52: |
Nowak et al. 2004 report on Chandra observations of IGR J00291+5934 with
HETG/ACIS-S.
Form their preliminary analysis, the authors improve the X-ray position of the source
to :
ra=00h 29m 03.08s ,
dec=Dec +59deg 34' 19.2"
(0.6" (??) +- 90% confidence)
further confirming the association of the X-ray source with the Optical counterpart reported in various
Atels (e.g. Fox and Kulkarni Atel 354)
The preliminary spectral analysis shows the source has a spectrum consistent
with an absorbed power law with Nh=2.8e21 +- 0.4e21 cm^-2, and Gamma = 1.9 +- 0.1
(90% confidence level).
The authors also confirm the decrease of X-ray flux as predicted earlier .
More details in Nowak et al. 2004 Atel 369
| Mail#51: |
Swank & Markwardt 2004 Atel 365 report an increasing decay
rate of this new millisecond X-ray pulsar, from RXTE monitoring
of the source.
See Swank and Markwardt 2004
Atel 365
Filippenko et al. 2004 Atel 366 report on Keck optical spectroscopy of the
same source.
They first confirm the association of the source reported by Fox and Kulkarni
(Atel 354) as the optical couterpart to IGR J00291+5934.
Their spectroscopic analysis reveals emission lines superposed to a blue continuum.
They report broad (FWHM = 1200 km/s) lines, identified as H-alpha (equivalent width 0.96 nm),
H-beta (EW = 0.54 nm),
He I 667.8nm (EW = 0.1 nm).
They also report a very faint narrow (FWHM = 300 km/s) feature identified as
He II 468.6 nm (EW=0.06nm)
More details in Filippenko et al. 2004 Atel 366
| Mail#50: |
Steeghs et al. 2004 ATel 363 report the detection of the infrared counterpart to
the outbursting millisecond pulsar IGR J00291+5934 with the 1.3m robotic PAIRITEL telescope.
The magnitudes of the source are J=16.8 +- 0.1, H=16.8 +- 0.3, K=16.1 +- 0.2.
These authors report a decay of brightness in observations performed a day later.
Using the FLWO 1.2m telescope on Mt. Hopkins, the same authors report an optical magnitude of
R=18.3 +- 0.4, significantly lower than during previous observations (Fox and Kulkarni, Atel 354)
Images are available at http://pairitel.org/IGRJ00291_5934
More details in Steeghs et al. 2004
Atel 363
In the mean time, Rupen et al. 2004 Atel 364, report on VLA observations of the radio counterpart
to the same source.
The flux of the source is 0.17 +- 0.05 mJy at 4.86 GHz, on dec 9, quite consistent with the
5GHz flux reported by Fender et al. Atel 361, which suggests the decay is not rapid.
More details in Rupen et al. 2004
Atel 364
| Mail#49: |
in 't Zand & Heise 2004 report on analysis of archival Beppo-Sax data.
Concerning IGR J11435-6109, these authors report that the source was
detected on 5 occasions. Analysing the longest exposure (net exposure
time of 212 ks), they improve the position to
ra=11h44m00.4s
Decl. = -61d07'16"
(+/- 1.4 arcmin @99%)
This position is consistent with the INTEGRAL position, and further suggests an
association with the ROSAT source 1RXS J114358.1-610736 as mentioned by Grebenev
et al. 2004 (Atel 350).
The spectrum is consistent with an absorbed power law with Nh~9(+-2)e22 cm-2
and Gamma=1.9 +-0.2.
in 't Zand & Heise confirm the pulsation found by Swank and Markwardt 2004 (Atel 359).
They refine the pulse period to 161.76 +- 0.01 sec.
According to them the outburst recurring time suggest an orbital period of 52.5 d, which
may indicate IGR J11435-6109 is an HMXB pulsar.
in 't Zand & Heise also report possible detection by the Einstein satellite in 1980 (as
2E 1141.6-6050).
Concerning the millisecond pulsar IGR J00291+5934, the authors report no detection from
a total of 2.9 Ms observations. They however note that the time of the ASM detection (Remillard
2004 Atel 357) were not covered by Beppo-Sax.
More details in in 't Zand & Heise 2004
Atel 362
| | Mail#48: | Fender et al. report on radio observations of the field of the INTEGRAL source IGR J00291+5934. They author report that no detection is achieved with the Ryle telescope any more down to a limit of 0.6 mJy (3 sig). On the other hand observation with the WSRT at 5 GHz reveal a 250 +- 35 microJy object at a position about 1" away from the optical counterpart. The author suggest a possible decrease of the radio flux during the observation. More details in Fender et al. 2004 Atel 361 | |
| Mail#47: | - Ron Remillard (Atel 357) reports on the result of an analysis of the RXTE/ASM long light curve of IGR J00291+5934. The light curve built at the position of the optical counterpart, shows the source entered the current outburst on december 2 2004, while in the past only marginal evidence is found for a similar outburst in 1998 November, and 2001 September. According to Ron, and provided these results are correct, the source may have a recurrence time of 3 years and the current outburst should not last very long. More Details in Remillard 2004 Atel 357 - Concerning the same source, Markwardt et al. Atel 360 report on further RXTE/PCA observations. They first say that the source flux has decayed. More importantly, they report the best period of the binary system to be 147.412 min (~2h 27 min). Assuming a mass of 1.4 Msun for the neutron star they show that the companion must have a mass > 0.038 Msun. More details in Markwardt et al. 2004 Atel 360 -Swank and Markwardt 2004 Atel 359, report on RXTE observations of IGR J11435-6109 (Grebenev et al. Atel 350). The authors report on the discovery of a possible pulsation with a period of 166 s. Their spectral analysis reveals Nh<1e23 cm-2 (3 sigma), and a photon index of 2.3 +-0.4 The source Luminosity was also an order of magnitude fainter than during the INTEGRAL observations More details in Swank and Markwardt 2004 Atel 359 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#46: | Further to the discovery of IGR J00291+5934 (Eckert et al. 2004, Atel 352), Markwardt et al. 2004 (Atel 353) report the discovery of X-ray pulsations with RXTE at a barycentric frequency of 598.88 Hz, with a pulsed amplitude of about 6%. Drifts in this period also suggest an orbital period (of a binary system) of about 2-4 hours. Spectral analysis of the XTE data reveal an absorbed power law spectrum, with Nh~7e21 cm-2, and Gamma=1.7. In the meantime Fox and Kulkarni (2004, Atel 354) possibly identified the optical (R band) counterpart to the X-ray source, at RA=00h 29m 03.06s, Dec=+59° 34' 19.0" (+-0.5"), with R~17.4. Guy Pooley (2004, Atel 355) report a 3.5 sigma detection of a radio source with the Ryle telescope, whose position is coincident with that of INTEGRAL and 12" away from that of the optical source (but the Ryle telescope resolution is 25" in this mode). The source flux is 1.1 mJy Finally Roelofs et al. (2004 Atel 356) report on optical spectroscopy of the afore mentioned possible optical counterpart with the ISIS spectrograph mounted on the 4.2m William Herschel Telescope (La Palma). These authors report weak evidence for broad emission line features near the HeII line (4686 A) and near the Halpha line (6563 A). According to them, this further support the identification of this object with the X-ray source. More details in : - Markwardt et al. Atel 353 - Fox and Kulkarni Atel 354 - Pooley Atel 355 - Roelofs et al Atel 356 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#45: | Eckert et al. report the discovery of a new source IGR J00291+5934 with the ISGRI detector onboard the INTEGRAL observatory. It was also detected by JEM-X in one pointing. The source is located at ra=00h 29.1' dec=+59d 34m (+- 1.5' 90% confidence) The source had A flux of 23+/-5 between 3 and 10 keV, and 55+/-5 mCrab between 20 and 60 keV. It will be in the INTEGRAL FOV again on dec. 5, for an open time observation More details in Eckert et al. 2004 Atel 352 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#44: | Capitanio et al. report on the analysis of INTEGRAL observations of the black hole candidate IGR J17464-3213/H1743-322, over its 2003 outburst. They study the evolution of the source in terms of spectral states, and show that the initial stage of the outburst where dominated by thermal comptonisation, while after the initial rise, the spectra showed the presence of a thermal component, with the hard X-ray luminosity unchanged though. 2 months later the source spectrum was dominated by a thermal component while the hard x-ray tail had a luminosity fainter by a factor of ~10. More details in Capitanio et al. accepted in ApJ (2005) Astro ph 0411790 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#43: | Grebenev et al. report the discovery of a new source IGR J11435-6109 with the ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=11h43m52s dec=-61d09m00s (2.5' @ 90% confidence) The authors report the probable association of this source with 1RXS J114358.1-610736. The source was also detected in the softer X-rays with the JEM X detector. More details in Grebenev et al . 2004, Atel 350 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#42: | Sidoli et al. report the very likely association of the ASCA source AX J161929-4945 with the INTEGRAL source IGR J16195-4945 (Walter et al. 2004, Atel 229). The results of the analysis of archival ASCA data show that the source is persistent although most of the time at a faint level of luminosity, is heavily absorbed with Nh~12 e22 cm-2, and has a rather hard spectrum. These results suggest the source is a neutron star HMXB. More details in Sidoli et al. accepted for publication in A&A letters Astro-ph 0411610 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#41: | Gotz et al. 2004, and Kretschmar et al. 2004 report the discovery of a new hard X-ray source IGR J17407-2808 with the IBIS/ISGRI detector onboard the INTEGRAL observatory. The source was discovered on October 9, as it was undergoing Hard X-ray flares. It is located at ra=17h 40.7m dec=-28s 08' (+-2.3' 90% confidence) The authors further report the association of this source with a faint ROSAT source labeled SBM 10/2RXP J174040.9-280852 Given the brightness of the flares, the source was first detected by the INTEGRAL Burst Alert System, but a GRB as the origine of the flare was soon dismissed. More details in Kretschmar et al. 2004 Atel 345 and Gotz et al. 2004 GCN2793 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#40: | Grebenev & Sunyaev report the discovery of a faint new source IGR J17507-2856 with the ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=17h50m44s dec=-28d56m17s (+-2' @90% confidence). They also exlcude the possible association of this source with other known nearby sources. More details in Grebenev & Sunyaev 2004, Atel 342 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#39: | Further to our report of a possible new INTEGRAL source yesterday (Atel 340), Halpern, & Gotthelf 2004, suggest that IGR J18410-0535 is the hard X-ray counterpart to the ASCA source AX J1841.0-0536. If this association holds then the best source position as derived with Chandra is ra=18h41m00.54s dec=-05d35'46.8" (0.6"(?) @ 90% confidence) In this case IGR 18410-0535 would be a Be X-ray binary hosting a pulsar The best coordinate of the likely optical/IR counterpart are ra=18h41m0s.43, dec= -05°35'46".5 and the derived magnitudes B=15.91, R=12.78, I=10.90, J= 9.74, H=9.22, K= 8.93 More details in Halpern, & Gotthelf Atel 341 (and Halpern et al. Atel 289) Atel 341 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#38: | We (Rodriguez et al. 2004) report the discovery of a possible new source IGR J18410-0535 with the IBIS/ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=18h 41.0m DEC.=-05deg 35 (+-2' @ 90% confidence) We point out that due to the proximity with IGR J18406-0539 (Molkov et al. 2004 Astron. Letters/ astro-ph 0402416), we cannot completely exclude that both sources are the same. More details in Rodriguez et al. (2004) Atel 340 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#37: | Reig et al. 2004 report the possible identification of the likely optical counterpart to IGR J01363+6610. The source is located at ra=01h35m50s dec=66deg 12'40" If this source is indeed the true counterpart, then through the spectral and photometric studies of this star, the author suggests that IGR J01363+6610 is a new Be/X-ray binary More details Atel 339 & 343 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#36: | Lutovinov et al. (A&A to be published in 2005) report on INTEGRAL observations of IGR J17091-3624, IGR/XTE J17391-3021, IGR J17464-3213, IGR J17597-2201, and SAX/IGR J18027-2017. The authors present spectral and temporal analysis of those sources and propose that: 1) IGR J17091-3624 & IGR J17464-3213 are Black Hole Candidates, the latter a possible LMXB 2) IGR J17391-3021 contains a neutron star, and is possibly an HMXB 3) IGR J18027-2017 contains a pulsar and is a possible HMXB 4) IGR J17597-2201 is burster, therefore a neutron star LMXB. More details in Lutovinov et al. (accepted in A&A), astro-ph 0407342 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#35: | Smith reports the identification of the optical counterpart to IGR J16465-4507 from the USNO B1 cat. Smith give a table of magnitudes of this blue supergiant (0448-0520455), and further suggest similarities with other IGR sources IGR J17544-261, and also IGR J17391-3021/XTE J1739-302, for which he also reports tabulated magnitude. More details in Smith 2004 Atel 338 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#34: | Zurita & Walter report follow-up observations of the INTEGRAL source IGR J16465-4507 with XMM-Newton. They identify a unique X-ray counterpart in the XMM error box located at ra=16h 46m 35.5s dec=-45deg 07' 04" (+-4" @ 90% confidence) Browsing the 2MASS catalogue these authors also report the identification of an infrared counterpart labeled 2MASS J16463526-4507045 with a J magnitude of 10.54 More details in Zurita & Walter 2004, Atel 336 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#33: | Masetti et al.
(2004) report Optical spectroscopy of 3 INTEGRAL sources
IGR J17303-0601, IGR J18027-1455, and IGR J21247+5058.
According to their analysis (it is very likely that):
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| Mail#32: | Lutovinov et al. (2004) report the discovery of a new source IGR J16465-4507 with the IBIS/ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=16h46.5m dec=-45o07.5m (+-2.5 arcmin @90% confidence) It is located at 16 arcmin from, another INTEGRAL source IGR J16479-4514, the latter being also detected at the same time. More details in Lutovinov et al. Atel 329 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#31: | Lutovinov et al. (2004) report the discovery of a new source IGR J17331-2406 with the IBIS/ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=17h33m08s dec=-24o06m46s (+- 2 arcmin @90% confidence) More details in Atel 328 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#30: | Filliatre & Chaty report the identification of the optical and Infra red counterpart of IGR J16318-4848 with observations from the NTT. They confirm the NIR counterpart proposed by Walter et al. 2003 (A&A 411, L427), and identify the optical counterpart to the source. Their NIR spectroscopy allowed them to reveal a large number of emission lines making IGR J16318-4848 similar to CI Cam. From their observations, Filliatre and Chaty propose the source is a HMXB located between 0.9 and 6.2 kpc, composed of a sgB[e] donor star. More details in Filliatre and Chaty 2004, accepted for publication in ApJ Astro-ph 0408407 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#29: | Rupen et al. report on VLA observations of the black hole candidate IGR J17464-3213 / H1743-322 / XTE J1746-322. Renewed activity is observed. The source has a flux density of 1.96 Â+- 0.15 mJy at 4.86 GHz on august 5 while no detection is achieved the previous day. The best radio position for the core inferred from their observations is: ra= 17 46 15.5980 +- 0.0050 dec= -32 14 00.80 +- 0.18 consistent with the previous position from Steeghs et al. 2003 (Atel 146), and Rupen et al. 2003 (Atel 137) More details in Rupen et al. 2004, Atel 314 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#28: | Combi et al. report some multiwavelength observations of the field around the 2 INTEGRAL sources IGR J18027-1455 and IGR J21247+5058. Their paper summarizes in fact what had been previously sent through different ATELs. The new thing is that they search for counterparts using the Bird et al. (2004, ApJL, 607, L33) gamma ray positions of the sources. The previously proposed counterparts are confirmed. More details in Combi et al. 2004, astro-ph 0408010 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#27: | Masetti et al. report optical observations of IGR J18027-1455.
They find that the source spectrum is consistent with that of an AGN, likely a Seyfert 1. They estimate a redshift z=0.036
More details
Atel 310
Cameron et al. report on radio observations of the whole field around IGR J00370+6122 using the VLA. They found no detection with the nominal flux densities measured at the position of BD +60 73: # 1.46 GHz: 0.34 +- 0.23 mJy/beam # 4.86 GHz: 0.055 +- 0.044 mJy/beam # 8.46 GHz: 0.081 +- 0.033 mJy/beam # 22.46 GHz: 0.44 +- 0.20 mJy/beam More details in Atel 312 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#26: | J. Swank reports
the X-ray rebrightening of IGR J17464-3213;
seen with RXTE/PCA and ASM.
Other RXTE observations are planned.
More details in Atel 301
In addition, Rupen et al. report on VLA observations of this black hole candidate. Nothing was detected recently (July 11, and June 27, 2004), whereas a possible (3 sig) detection is reported for April 9 2004. More details in Atel 304 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#25: | Hannikainen et al. report on INTEGRAL observations of IGR J19140+0951, at the time of its discovery (revolution 48). From the analysis of joint JEM-X+ISGRI spectra they identify two "spectral" states, one with a thermal component (black body), and a powerlaw tail, the other dominated by thermal comptonisation. The authors suggest that IGR J19140+0951 is a Galactic X-ray binary, probably hosting a neutron star primary, although the possibility of a black hole cannot be ruled out. more details in Hannikainen et al. (2004, to be published in A&AL) Preprint | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#24: | Negueruela & Reig 2004 report optical observations of BD +60 73 (Optical counterpart to IGR J00370+6122) with the 2.5 Isaac Newton Telescope They derive a spectral type of BN0.5II-III for this star. They thus propose a preliminary distance to the source of 3 kpc. They further suggest that the low X-ray luminosity could result from a low wind density accretor in an eccentric orbit. More details in Negueruela & Reig 2004 Atel 285 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#23: | B. Monard (Bronberg Observatory / CBA Pretoria) reports on observations of the field around IGR J11305-6256, through the VSNET collaboration. He possibly identified an optical counterpart to IGR J11305-6256. His report can be found here | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#22: | den Hartog et al. 2004
report the discovery of a new source IGR J00370+6122 with the ISGRI detector
onboard the INTEGRAL observatory. The source is located at
ra=0h 37m 05.4s
dec=+61o 22' 13"
(+-2 arcmin at 90% confidence)
They also report identification of X-ray (1RXS J003709.6+612131) and optical (BD +60 73) counterparts to this source, and a X-ray periodicity
of 15.665 Â+- 0.006 days using RXTE/ASM data.
From their analysis they suggest the source is a new HMXB.
more details in den Hartog et al. 2004
Atel 281
In addition Rutledge 2004, confirms the association of the Rosat source with BD +60 73, with a probability of a unique identification of 99.7% more details in Rutledge 2004 Atel 282 Atel 282 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#21: | Produit et al. 2004 report the discovery of a new source IGR J11305-6256 with the ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=11h30m34s dec=-62d55m51s (+-5' 90% confidence) more details in Produit et al. 2004 Atel 278 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#20: | Grebenev et al. 2004 report the discovery of a new source IGR J01363+6610 with the ISGRI detector onboard the INTEGRAL observatory. The source is located at ra=01h36.3m, Decl.=+66d10.5' (+- 2' at 90% confidence) The source is also detected in JEM X. more details in Grebenev et al. 2004 Atel 275 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#19: | Cabanac et al. 2004 report a revised and improved position of IGR J19140+0951 (formerly knwon as IGR J19140+098) using both the Jem X2 and IBIS/ISGRI detectors onboard the INTEGRAL observatory. The new position is ra=19h 14m 02s dec=+09deg 53.3' (+-1.3 arcmin 90% confidence) at about 2.4 arcmin from the position obtained using an early version of the INTEGRAL analysis software (IAUC 8088). more details in Cabanac et al. 2004 Atel 272 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#18: |
Chaty & Filiatre (2004) report Optical and Near Infra red observations
of the higly absorbed source IGR J16318-4848.
They report the discovery of the optical counterpart to the source,
and confim the NIR counterpart of Foschini et al. 2003 (IAUC 8076).
Based on their study, Chaty & Filiatre propose that IGR J16318-4848 is
an HMXB with a sgB[e] companion.
In this case IGR J16318-4848 is the second sgB[e] X-ray Binary after
CI Cam.
More details in Chaty & Filiatre (2004) .
astro-ph 0404332
Schultz et al. (2004), report on RXTE, INTEGRAL and NOT observations of IGR J19140+0951. They report spectral transitions between steep power law and hard states. They therefore suggest that IGR J19140+0951 could host a black hole rather than a neutron star. more details in Schultz et al. (2004) astro-ph 0404327 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#17: | Corbet et al. 2004 report the discovery a strong modulation of the RXTE/ASM flux of IGR J19140+098 at a period of 13.55 days. They propose that this period is the orbital period of an X-ray Binary. They also report the detection of the modulation during the first years of observation with the ASM, indicating the activity of the source at that time. More detail in Corbet et al. 2004 Atel 269 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#16: | Molina et al. 2004 report the possible identification of an near infra red counterpart to IGR J07597-3842 (ATEL 261). The object (J075941.8-384356) has magnitudes J=13.560, H=12.465 and K=11.345, it is also reported with I=15.026-15.114, R=14.2 and B=16.6 These author further suggest that the source is an AGN more details in Molina et al. 2004 Atel 263 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#15: | den Hartog et al. 2004 report the discovery of a new source IGR J07597-3842 with the detector IBIS/ISGRI onboard the INTEGRAL observatory. The source is located at ra=7h 59m 43.5s dec=-38o 42' 36s (2 arcmin) The spectrum is power law like with a photon index 1.8 +/-0.3. den Hartog et al. discuss also the possible identification of soft X-rays, IR and radio counterparts to this source. They propose the source is an AGN, although a Galactic origin cannot be ruled out. More details in den Hartog et al. 2004, Atel 261 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#14: | Rodriguez et al. 2004 report Chandra HRC-I observations of the field around IGR J16316-4028. The source is not detected with a 3-sig upper limit of 5E-14 erg/cm2/s. They further report the spectral analysis of the IBIS/ISGRI data from the discovery of the source (see Atel 201). These observations suggest that IGR J16316-4028 was flaring at the time of its discovery, and has now returned to quiescence. More details in Rodriguez et al. 2004, Atel 253 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#13: | Grebenev et al. 2004 report the detection of a new outburst from the INTEGRAL source IGR J17544-2619 (Atel 190 , 192 , 194, IAUC 8202 , A&A 2004/astro-ph 0402293 ) with the IBIS/ISGRI and JEM-X detectors onboard the INTEGRAL observatory. This renewing acivity suggests IGR J17544-2619 is a recurrent transient. more details in Grebenev et al. 2004, Atel 252 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#12: | Combi et al. 2004 report the possible Radio, IR and soft X-ray counterpart to IGR J18027-1455 (Walter et al. Atel 229). They found two radio sources in the INTEGRAL error box. The second one falls well within the ROSAT error box of 1RXS J180245.5-145432. Inside the radio error box is also located an extended IR source. More details in Atel 246 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#11: | Molkov et al. report the discovery of 3 new sources IGR J18490-0000, IGR J18406-0539, and IGR J18450-0435 with the ISGRI detector onboard the INTEGRAL observatory. IGR J18490-0000 is located at ra=18h 49.0 min dec=0°0' (2-3' 90% confidence) IGR J18406-0539 is located at ra=18h 40.6 min dec=-5°39' (2-3' 90% confidence) IGR J18450-0435 is located at ra=18h 45.0 min dec=-4°35' (2-3' 90% confidence) They also report the detection of an additional possible one IGR J19378-0617, although they cannot completely exclude the source is in fact SS 442. more details in Molkov et al 2004 astronomy letters astro-ph0402416 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#10: | Ribo et al. 2004 report the identification of a radio galaxy as a possible counterpart to IGR J21247+5058. more details in Atel 235 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#9: | Gonzalez-Riestra et al. 2004 report XMM Observations of the INTEGRAL source IGR J17544-2619 (Sunyaev et al. 2004 Atel 190). They improve the position of the source to ra= 17h 54m 25.37s dec=-26° 19' 52.9" (+-4" 90% confidence) They obtain Nh of the order of 1-2e22 cm-2, compatible with the interstellar value. They also confirm the possible association of 2MASS J 17542527-261926 (Rodriguez et al. 2003, Atel 194) with the X-ray source. Their analysis leads to the conclusion that the companion may be an early O type star, without excluding, however, a foreground object. More details in Gonzalez-Riestra et al. 2004, A&A in press, astro-ph0402293 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#8: | Walter et al. 2004 report the discovery of 14 new sources with the ISGRI detector onboard the INTEGRAL observatory. IGR J16167-4957 ra=16:16.7 dec=-49:57, IGR J16195-4945 16:19.5 -49:45, IGR J16207-5129 16:20.7 -51:29, IGR J16558-5203 16:55.8 -52:03, IGR J17195-4100 17:19.5 -41:00, IGR J17200-3116 17:20.0 -31:16, IGR J17252-3616 17:25.2 -36:16, IGR J17254-3257 17:25.4 -32:57, IGR J17285-2922 17:28.5 -29:22, IGR J17303-0601 17:30.3 -06:01, IGR J17460-3047 17:46.0 -30:47, IGR J17488-3253 17:48.8 -32:53, IGR J18027-1455 18:02.7 -14:55, IGR J21247+5058 21:24.7 +50:58, Uncertainty about 2 arcmin More details in Walter et al 2004, Atel 229 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#7: | Revnivtsev et al. 2004 report the discovery of two new sources IGR J17475-2822 and IGR J18027-2016 with the ISGRI detector onboard the INTEGRAL observatory. The first source is located at ra=17h 47.5m, dec=-28deg 22' (2-3' error). Note that due to its location (0.7 deg from the Galactic center), this source could be a superimposition of several weaker sources. The second source is located at ra=18h 02.7m, dec=-20deg 16' (2-3' error). More details in Revnivtsev et al 2004, astro-ph 0402027 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#6: | G. Pooley report a possible association of the radio source NVSS J060718+220452 with IGR J06074+2205. An unresolved source is also detected with the Ryle Telescope. More details in Atel 226 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#5: | A. Malizia et al. 2004 report the discovery of a source IGR J16393-4643 with the IBIS/ISGRI detector onboard the INTEGRAL observatory. The source is located at ra= 16h39.3m, dec= -46o 43 (+-2 '). The source lies in the 90% error box of the Egret source 3EG J1639-4702, which might indicate that IGR J16393-4643 is the x-ray counterpart to the Egret source. The Asca source AX J1639.0-4642 is well within the INTEGRAL error box, which renders the identification of IGR J16393-4643 with the Asca source very likely. more details in Atel 226 Note that a (submitted) paper by Combi et al. reporting multiwavelength study of the field of AX J1639.0-4642 is available on astro-ph. astro-ph 0402027 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#4: | Tomsick et al. 2004 report the discovery of 2 new sources IGR J15479-4529 and IGR J16418-4532 with the IBIS/ISGRI detector onboard the INTEGRAL observatory. IGR J16418-4532 is located at ra=16h41.8, dec=-45deg32', (+-2'). It belongs to the "group" of the several sources found in the Norma region. IGR J15479-4529 is located at ra=15h47.9, dec=-45deg29', (+-2'). The latter might be associated with 1RXS J154814.5-452845. More details in Atel 224 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#3: | Chevenez et al. 2004 report the discovery of a new source IGR J06074+2205 with both JEM- X detectors onboard the INTEGRAL observatory, and a clear detection with the imager IBIS/ISGRI. The source is located at ra= 06h07.4m, dec=22°05' +-2'. It lies ~8 deg from the Crab. More details in Atel 223 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#2: | Cabanac et al. have done some work based on INTEGRAL (JEMX and ISGRI) data and one RXTE observation of IGR J19140+098. According to them the source is most likely to be a Galactic X-ray Binary than an AGN. The type of the compact object is still uncertain, however. Their work will be published in a conference proceedings. See astro-ph 0401308 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mail#1: | I inform of the detection of a source labeled IGR J17456-2901 by Belanger et al. (2004). This source is consistent with the Galactic nucleus to within 0.9 arcmin. It is thus the first significant detection of hard X-ray emission (20-100 keV) from the inner 10 arcmin from the Galactic Center. Discussion on source confusion in this crowded region is also presented in the paper. See Belanger et al. 2004, ApJ, 601, L163 preprint | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
