Unveiling Supergiant Fast X‐Ray Transient Sources withINTEGRAL

Supergiant high mass X-ray binaries (SGXBs) are believed to be rare objects,as stars in the supergiant phase have a very short lifetime and to date onlyabout a dozen of them have been discovered. They are known to be persistent andbright X-ray sources. INTEGRAL is changing this classical picture as itsobservations are revealing the presence of a new subclass of SGXBs which havebeen labelled as supergiant fast X-ray transients (SFXTs) as they are stronglycharacterized by fast X-ray outbursts lasting less than a day, typically a fewhours. We report on IBIS detections of newly discovered fast X-ray outburstsfrom 10 sources, four of which have been recently optically identified assupergiant high mass X-ray binaries. In particular for one of them, IGRJ11215-5952, we observe fast X-ray transient behaviour for the first time. Theremaining six sources (IGR J16479-4514, IGR J16418-4532, XTE J1743-363, IGRJ16195-4945=AX J161929-4945, AX J1749.1-2733, IGR J17407-2808) are stillunclassified, however they can be considered as candidate SFXTs because oftheir similarity to the known SFXTs.Comment: 46 pages, 21 figures, 6 tables, accepted for publication in Ap