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Post Info TOPIC: IGRJ16479-4514
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IGR J16479-4514
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Title: A Suzaku X-ray observation of one orbit of the supergiant fast X-ray transient IGR J16479-4514
Authors: L. Sidoli (INAF-IASF Milano, Italy), P. Esposito, V. Sguera, A. Bodaghee, J.A. Tomsick, K. Pottschmidt, J. Rodriguez, P. Romano, J. Wilms

We report on a 250 ks long X-ray observation of the supergiant fast X-ray transient (SFXT) IGR J16479-4514 performed with Suzaku in 2012 February. About 80% of the short orbital period (Porb=3.32 days) was covered as continuously as possible for the first time. The source light curve displays variability of more than two orders of magnitude, starting with a very low emission state lasting the first 46 ks (1E-13 erg/cm²/s, 1-10 keV), consistent with being due to the X-ray eclipse by the supergiant companion. The transition to the uneclipsed X-ray emission is energy dependent. Outside the eclipse, the source spends most of the time at a level of (6-7)x10^-12 erg/cm²/s punctuated by two structured faint flares with a duration of about 10 and 15 ks. Remarkably, the first faint flare occurs at a similar orbital phase of the bright flares previously observed in the system. This indicates the presence of a phase-locked large scale structure in the supergiant wind, driving a higher accretion rate onto the compact object. The scattered component visible during the X-ray eclipse allowed us to directly probe the wind density at the orbital separation, resulting in rho=7E-14 g/cm³. Assuming a spherical geometry for the supergiant wind, the derived wind density translates into a ratio Mdot_w/v_terminal = 7E-17 solar masses/km which, assuming terminal velocities in a large range 500-3000 km/s, implies an accretion luminosity two orders of magnitude higher than that observed. As a consequence, a mechanism is at work reducing the mass accretion rate. Different possibilities are discussed.

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Blobrana


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Posts: 131433
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IGRJ16479-4514
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Title: Swift observations of IGRJ16479-4514 in outburst
Authors: E. Bozzo, A. Giunta, L. Stella, M. Falanga, G. Israel, S. Campana

The supergiant fast X-ray transient source IGR J16479-4514 was observed in outburst two times with Swift. Its quiescent state was investigated in-depth only once in 2008 through a relatively long pointed observation with XMM-Newton. The latter observation was taken about 1.7 days after the outburst in 2008, and showed an X-ray eclipse-like event, likely caused by the supergiant companion. At present, this is the only supergiant fast X-ray transient that displayed an evidence for an X-ray eclipse. Here we carry out a comparison between the most recent outburst of IGRJ16479-4514, caught by Swift on 29 January 2009 and those detected previously from this source. The decay from the outbursts in 2005, 2008 and 2009 presents many similarities, and suggests a common mechanism that modulates the mass accretion rate onto the neutron star in IGRJ16479-4514.

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Blobrana


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Title: The first X-ray eclipse of IGRJ16479-4514?
Authors: E. Bozzo, L. Stella, G. Israel, M. Falanga, S. Campana

We report on the first long (~32 ks) pointed XMM-Newton observation of the supergiant fast X-ray transient IGRJ16479-4514.
Results from the timing, spectral and spatial analysis of this observation show that the X-ray source IGRJ16479-4514 underwent an episode of sudden obscuration, possibly an X-ray eclipse by the supergiant companion. We also found evidence for a soft X-ray extended halo around the source that is most readily interpreted as due to scattering by dust along the line of sight to IGRJ16479-4514.

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Blobrana


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Title: IGRJ16479-4514: the first eclipsing supergiant fast X-ray transient?
Authors: E. Bozzo, L. Stella, G. Israel, M. Falanga, S. Campana
(Version v2)

Supergiant fast X-ray transients are a new class of high mass X-ray binaries recently discovered with INTEGRAL. Hours long outbursts from these sources have been observed on numerous occasions at luminosities of ~1E36-1E37 erg/s, whereas their low level activity at ~1E32-1E34 erg/s has not been deeply investigated yet due to the paucity of long pointed observations with high sensitivity X-ray telescopes. Here we report on the first long (~32 ks) pointed XMM-Newton observation of IGR J16479-4514, a member of this new class. This observation was carried out in March 2008, shortly after an outburst from this source, with the main goal of investigating its low level emission and physical mechanisms that drive the source activity. Results from the timing, spectral and spatial analysis of the EPIC-PN XMM-Newton observation show that the X-ray source IGRJ16479-4514 underwent an episode of sudden obscuration, possibly an X-ray eclipse by the supergiant companion. We also found evidence for a soft X-ray extended halo around the source that is most readily interpreted as due to scattering by dust along the line of sight to IGRJ16479-4514. We discuss this result in the context of the gated accretion scenarios that have been proposed to interpret the behaviour of supergiant fast X-ray transient.

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Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: IGRJ16479-4514: the first eclipsing supergiant fast X-ray transient?
Authors: E. Bozzo, L. Stella, G. Israel, M. Falanga, S. Campana

Supergiant fast X-ray transients are a new class of high mass X-ray binaries recently discovered with INTEGRAL. Hours long outbursts from these sources have been observed on numerous occasions at luminosities of ~1E36-1E37 erg/s, whereas their low level activity at ~1E32-1E34 erg/s has not been deeply investigated yet due to the paucity of long pointed observations with high sensitivity X-ray telescopes. Here we report on the first long (~32 ks) pointed XMM-Newton observation of IGR J16479-4514, a member of this new class. This observation was carried out in March 2008, shortly after an outburst from this source, with the main goal of investigating its low level emission and physical mechanisms that drive the source activity. Results from the timing, spectral and spatial analysis of the EPIC-PN XMM-Newton observation show that the X-ray source IGRJ16479-4514 underwent an episode of sudden obscuration, possibly an X-ray eclipse by the supergiant companion. We also found evidence for a soft X-ray extended halo around the source that is most readily interpreted as due to scattering by dust along the line of sight to IGRJ16479-4514. We discuss this result in the context of the gated accretion scenarios that have been proposed to interpret the behaviour of supergiant fast X-ray transient.

Read more (64kb, PDF)

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