Observational properties of candidate supergiant fast X-ray transients

Abstract

INTEGRAL allowed the discovery of several new SuperGiant X-ray Binaries of which very few were known before its launch. Among them, INTEGRAL has unveiled a new sub-class: galactic X-ray sources with a supergiant companion and displaying a transient behaviour, namely Supergiant Fast X-ray Transient. Most of the time in quiescence with a luminosity of 10 33 erg s −1 (if not totally absent), these sources display rare episodes of short (few ks) and bright (up to ∼ 10 36 erg s −1 as in other SGXB) flares. Several scenarii have been proposed to explain the atypical temporal behaviour of the SFXT among the SGXB: a different separation/geometry of their orbits, accretion of dense structures/clumps formed in the stellar wind that would produce these huge flares, magnetic centrifugal barrier and variation of the local stellar wind density and/or sources hosting a magnetar. We present a systematic study, based on ISGRI observations from 2 ks-bin lightcurves to deep mosaics, of the observational properties (flares, duration, fluxes, etc.) of two SFXT candidates in order to bring constraints, to be able to distinguish between these different models of emission. Finally, this study will allow to better understand the overall characteristics of different classes of high-mass X-ray binaries. 7th INTEGRAL Workshop