INTEGRAL observations of recurrent fast X-ray transient sources
Hill, A. B.; Bird, A. J.; Ubertini, P.; Malizia, A.; Bazzano, A.; Clark, D. J.; Dean, A. J.; Sguera, V.; Willis, D. R.; Shaw, S. E.; Barlow, E. J.; Moran, L.
United Kingdom, Switzerland, Italy
Abstract
Fast X-ray Transients (FXTs) are believed to be non-recurrent bright X-ray sources lasting less than a day and occuring at serendipitous positions, they can best be detected and discovered by instruments having a sufficiently wide field of view and high sensitivity. The IBIS/ISGRI instrument onboard INTEGRAL is particularly suited to detect new or already known fast X-ray transient sources. We report on IBIS/ISGRI detection of newly discovered outbursts of three fast transient sources located at low Galactic latitude: SAX J1818.6-1703; IGR J16479-4514; IGR J17391-302/XTE J1739-302. The reported results confirm and strengthen the very fast transient nature of these sources, given that all their newly detected outbursts have a duration less than ~3 h. Additionally, they provide the first evidence for a possible recurrent fast transient behaviour as all three sources were detected in outburst by ISGRI more than once during the last 2 years.