| Miscellaneous :
| Smith 2004 (Atel 338): Optical magnitudes (USNO B1.0): B2=17, R2=12.9, possible
| Sguera et al. 2005 : |
- Fast transient
- Recurrent outburst
- Flares lasting between 30 minand 3 hours
- The source spectrum is typical of a NS binary
- Most likely a HMXB given counterpart but outbursts shorter than expected for HMXBS
or Be/NS binaries.
| Smith et al. 2005 : |
- During both low level and outburst states high energy spectra are hard.
- absorption column density seen to vary from one outburst to another.
- Class of Supergiant Fast Xray Transient
| Negueruela et al. 2005 : |
- Companion is O8 Iab(f) supergiant
- distance 2.3 kpc
| Sguera et al. 2006
- 20-60 keV peak flux of 480 mCrab
- outburst from 30 min to 14 hours duration
| Türler 2007 (Atel 1019):
- one of the brightest outbursts ever recorded occured at UT:13:30 on March 2, 2007.
- ~1-hour long outburst with peak fluxes of 330 and 250 mCrab in the 20-40 and 40-80 keV bands, respectively.
- thermal bremsstrahlung model with kT ~ 22.5 keV fits the 20-100 keV spectrum.
| Chaty et al. 2008:
- Optical and infrared observations
- 2MASS source is a blended source
- B>21.2, V=14.97, R=12.94, I=11.28, Z=10.458
- Discrepancy of IR mag with 2MASS cat due to domain of non linearity
of SOFI detector on NTT.
- Hα, Paschen H lines, HeI, HeII, NI lines in optical, and
IR spectra very rich in H lines.
- P-Cygni profile=> O sg, not a Be as stated in Bird et al. 2006
| Rahoui et al. 2008:
- Medium infrared observations, GLIMPSE data
- SED fitting => AV=9.2, Tstar=31400 K
- No need for an additional component to fit MIR spectra
- Suggested distance 2.7 kpc
| Romano et al. 2008:
- New outburst detected by Swift/BAT on
2008-04-08 at 21:28:15
- 15-150 keV BAT lightcurve nearly constant from T-119 to T+950 s
- BAT spectra simple power laws with photon indices ~constant (2.7 and 3.0).
- Swift/XRT light curve <=> 2 distinct flares the 2nd half bright
as the first. Photon indices harder than those from BAT spectra.
| Chenevez et al. 2008:
- INTEGRAL: outburst detected by Swift started in reality
5 hours earlier than the BAT trigger (2008-04-08)
- JEM-X detected a flare starting at 16:18
- 3-10 keV (resp 10-25 keV) mean flux averaged over ~2 hours was 42 mCrab
(resp. 80 mCrab).
- 3-10 keV (10-25 keV) upper limits before the flare were 4 mCrab (resp. 8 mCrab).
- Detection by ISGRI with 20-40 keV (40-80 keV)
fluxes of 31 mCrab (13 mCrab) over a 8 ksec observation.
| Sidoli et al. 2008:
- Swift study of the "out-of-outburst" periods
- Absorbed pl or bbody fits the data well
- Γ= 1.4 and NH=3.3x1022cm-2 or kT=1.5 keV and
| Blay et al. 2008:
- Analysis of INTEGRAL data (GPS, GCDE and
data from the Galactic centre key project from AO 4 and 5)
- Long term light curves of the source=>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
- No coherent modulation up to 100 s.
- Spectra: in addition to an absorbed exponentially cut-off power law
continuum, presence of broad absorption at 30 and 60 keV
- Cyclotron Resonant scatering feature to the continuum does not improve the fit significantly.
wind models explain well the properties of the source => predict an orbital period of ~8 days.
| Romano et al. 2008:
- New outburst seen with swift
- 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
| Sidoli et al. 2008:
- Swift monitoring => observation of 1 flare
- Spectrum has Γ=1.5 and is higly absorbed
(NH=13 x1022 cm-2).
- Compared to the out-of-outburst periods, the spectrum
has similar continuum but is more absorbed
- Broad band spectrum <=> power law
- Possible cut-off at 13 keV <=> Comptonization with kT=8 keV and τ=6.8
but same χ2 as for simple power law
- B comptible with 2 x1012 G => difficut to
reconcile with high B required by Bozzo et al.'s model
| Sidoli et al. 2009
- Time resolved spectroscopy of the flaring event
of 2008 August 13
- Spectra are well fitted with either an absorbed
power law or absorbed black body
- Values of the photon index or the black body temperature
- Clear evolution of the absorption column density: NH higher
during the rising portion of the flare
- bmc also used => bb temperature (of the seed photons) of 1.6 keV
for a black body size of 1.6 km => consistent with the size of
the polar cap
| Romano et al. 2009
- Swift analysis of the first year of monitoring
- Complete spectral analysis of the data => spectra well fitted with either an
absorbed power law or an absorbed black body
- Study of UVOT light curves
- duty cycle of inactivity = 39% => true quiescence is a rare state
| Bozzo et al. 2010
- XMM analysis during quiescence
- Quiescent emission composed
of multiple flares occuring after period of faint X-ray emission.
- Hardness ratio and the intensity are positively correlated
- Spectral analysis => soft component below 2 keV, in addition to
a standard (cutoff) power law with absorption
- Excess well represented by either a black body or thermal plasma model
- Thermal plasma could be the X-ray emission
due to shocks in the wind of the supergiant companion.
| Drave et al. 2010
- 51.47 d period in analysis of 12.4Ms of INTEGRAL data
- Interpreted as the orbital period of the system
- Observation of 35 epochs of outburst throughout orbit
- Source is not powered by Roche lobe overflow
- Semi major axis within 173.4-179.8 Rsun => eccentricities up to 0.8
- Neutron star probably orbits in an inhomogeneous clumpy wind
- Possibility of enhanced equatorial density region
| Romano et al. 2011:
- 2 years of Swift monitoring
- duty cycle of inactivity ~ 39%
- X-ray spectroscopy in different luminosity phases of activity
| Bodaghee et al. 2011:
- Suzaku observation
- First half in a dormant state <=> quiescence, absorbed luminosity of 1.3e33 erg/s (d/2.7 kpc)^2
- Second half in low-activity state with weak flares. Peak luminosity of 7.4e33 erg/s
- During flaring phase NH ~4.1e22 /cm2 <=> increase of a factor of 2--4 (compared toquiescence) =>
accretion of obscuring clumps of wind.
- Low state represents ~60% of all observations => most common behavior in this source.
| Farinelli et al. 2012 (MNRAS):
- Swift observations
- Spectral fits and interpretation within framework of comptonisation
| Wang & Chang 2012 (A&A):
- Characteristic time scale of variability 1550-2000 s
- Study retrograde wind accretion scenario
- asuming variability ~spin and orbital period => R corrotation ~ 1.3-1.6e10 cm.
- Uncertain nature of accretion regime