2014MNRAS.439.2175D -
Mon. Not. R. Astron. Soc., 439, 2175-2185 (2014/April-1)
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619.
DRAVE S.P., BIRD A.J., SIDOLI L., SGUERA V., BAZZANO A., HILL A.B. and GOOSSENS M.E.
Abstract (from CDS):
XMM-Newton observations of the supergiant fast X-ray transient IGR J17544-2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272±0.0004d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM-Newton observations (each lasting ∼ 15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544-2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033 erg/s (0.5-10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544-2619 dropped to ∼ 4x1032 erg/s (0.5-10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544-2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544-2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the `quasi-spherical accretion' model provides a good description of the behaviour of IGR J17544-2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.
Abstract Copyright:
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)
Journal keyword(s):
accretion, accretion discs - stars: winds, outflows - X-rays: binaries - X-rays: individual: IGR J17544-2619
CDS comments:
In chap 1 : IGR J16465-4514 is a misprint for IGR J16465-4507. In chap. 2 and 4 : IGR J16418-4514 are misprints for IGR J16418-4532
Simbad objects:
10
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