With the ROSAT-HRI, we have accurately determined the position of KS 1731-260 and showed that its error box does not contain any of the two proposed optical counterparts. On the other hand, our infrared imaging of the HRI error box reveals a large number of possible counterparts, all arguing in favour of a low mass system. H band spectroscopy could be performed and should eliminate some of them and reveal the true counterpart of the source. KS 1731-260 which is a persistent X-ray source since at least 1988 is going to be observed with RXTE during the second cycle of the guest investigator program. These observations will be useful is several ways; first to address the origin of possible intrinsic NH variations within the system (obscuration of the X-ray source by a disk corona, the outer disk, etc..). Secondly X-ray burst studies might help us to set even better constraints on the source distance and confirm the recent detection of millisecond pulsations.
© European Southern Observatory (ESO) 1998
Online publication: December 16, 1997