出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Supergiant Fast X–ray Transients (SFXTs) represent the most extreme case of X–ray variability in High Mass X-ray Binaries hosting blue supergiant companions. Mainly discovered thanks to the INTEGRAL monitoring of the Galactic plane, these hard X-ray transients display dynamic ranges which can span five orders of magnitude. This intensity variability is associated with accretion onto Galactic compact objects (mostly neutron stars) through a physical mechanism which is still poorly understood. A review of the current status of our understanding on these sources is presented and discussed. Finally, I present recent XMM-Newton results about the SFXT IGR J16418–4532, proposing that its variability behavior is due to a transitional accretion regime, intermediate between pure wind accretion and Roche Lobe Overflow. This same regime could explain the X–ray activity of other “intermediate” SFXTs with narrow orbits.
