IGR J 16479 - 4514 : the first eclipsing supergiant fast X - ray transient ?

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 ∼10-10 erg s, whereas their low level activity at∼10-10 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 XMMNewton observation show that the X-ray source IGR J16479-4514 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 IGR J16479-4514. 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.