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| Miscellaneous :
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Swank & Markwardt 2003 Atel 128
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- NH=~6 x 1022 cm-2
- Fe Line eq. width 550 eV in RXTE/PCA
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Corbet et al. 2004 Atel 269:
- Sinusoidal modulation of the RXTE/ASM flux with a period of 13.55 days
- Activity detected with RXTE/ASM as early as 1996
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Hannikainen et al. 2004 A&A, 423, L17:
- (At least) Two Spectral states: one with thermal component and power law tail, one characteristic of thermal Comptonisation
- INTEGRAL/ISGRI image of the field available here
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Rodriguez et al. 2005 A&A, 432, 235:
- Spends most of its time in a faint luminosity state characteristic of thermal Comptonisation
- Variations of NH up to ~1023 cm-2
- Iron line of variable intensity
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in't Zand et al. 2006 A&A:
- Flux lower than any INTEGRAL obs. but twice as high as all RXTE from Rodriguez et al.
2005
- Ks~8.7, I~13.0, V> 18.8
- Possible pulsation at 6.5 ks, but need confirmation
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Wen et al. 2006 :
Pulsation from RXTE/ASM confirmed at P=13.552d
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Rodriguez al. 2006 (ATel 800):
- RXTE/PCA and Swift/XRT => faintest state ever observed
- 1-20 flux is 1.54 x10-11 erg/s/cm2(Swift normalization),
- 1-20 keV unabsorbed flux is 2.47 x10-11 erg/s/cm2
- amplitude of X-ray flux variations of at least a factor 150 between different observations
- Another member of class of heavily absorbed sources
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Nespoli et al. 2007 (ATel 983):
- HeI and NIII/CIII in emission (weak for the later)
- HeI and Br-gamma in absorption
- absence of HeII
- B1 supergiant
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Hannikainen et al. 2007 MNRAS:
- K- and H-band spectra analyzed
- Spectral lines 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.
- Confirm the supergiant nature of the star, tweak the spectral classification to B0.5.
- Distance of 5 kpc is estimated. A B0.5 supergiant
- Supports the Sagittarius arm location
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Chaty et al. 2008: - Near infrared observations
- J=11.32, H=9.73, Ks=8.84
- IR spectra dominated by Paschen and Brackett H, HeI and He II
emission lines
- NIR spectra typical of O/B star, and lines of supergiant.
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Rahoui et al. 2008: - Medium infrared observations and GLIMPSE data
- MSX object given by in't Zand is a blnd of sources
- SED fitting => AV=16.5, T*=22500 K
- No need for additional component to fit spectra
- Suggested distance 3.1 kpc
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Nespoli et al. 2008: - Infrared spectroscopy
- B0.5 Iab
- Distance 1.1 (-0.8 +2.3) kpc
- Local absorption comes from material concentrated around the compact object
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Prat et al. 2008: - Spectral analysis of34 simultaneous RXTE and INTEGRAL observations
- Fits with absorbed power law, plus high energy cut off when required, and
absorbed comptonization model
- Spectral parameters => system very likely hosts a neutron starE
- Evolution of NH strongly correlated with the
orbit of the system => compact object deeply embedded in the wind of the companion
- Wind mass-loss rate of ~5 E-8 solar masses/year and orbital inclination ~ 38-75 degrees.
- Soft excess in 4 observations, at orbital phases consistent with
the neutron star being behind the companion => interpreted as
reprocessing of the X-ray emission originating from the neutron star by the surrounding ionised gas
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Torrejón et al. 2009:
- Optical spectroscopy
- Companion is a Sg B0.5 Ia star
- distance 3.6 kpc
- Typical Sg-HMXB
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Sidoli et al. 2016 (MNRAS):
- Discovery of 1.46 mHz QPO (and higher harmonics) during an XMM-Newton observation
- Re-analysis of a Chandra archival observation => modulation at 0.17+/-0.05mHz,
very likely NS spin period (although a QPO cannot be excluded)
- Faintest X-ray state observed (2e-12 erg/cm2/s, 2-10 keV, XMM data)
- Duty cycle (INTEGRAL archive) => system intermediate between persistent supergiant HMXBs and SFXTs.
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