INTEGRAL monitoring of the Galactic Plane is revealing a growing number of recurrent X-ray transients, characterised by short outbursts with very fast rise times (~ tens of minutes) and typical durations of a few hours. Here we show that several of these transients are associated with OB supergiants and hence define a new class of massive X-ray binaries which we call Supergiant Fast X-ray Transients (SFXTs). Many other transient X-ray sources display similar X-ray characteristics, suggesting that they belong to the same class. Since they are difficult to detect and their number is growing fast and steadily, they could represent a major class of X-ray binaries.
The X-ray Universe 2005
- Pub Date:
- January 2006
- To appear in Proceedings of "The X-ray Universe 2005", held in San Lorenzo de El Escorial (Madrid, Spain), 26-30 September 2005, ESA-SP 604. 6 pages, 6 figures, style file included