Chandra localization of KS1731--260

Abstract

We present the analysis of the Chandra image of KS 1731-260. The improvement of the source localization (down to ~0.6'') allowed us to rule out 12 of 13 infrared companion candidates proposed by Barret et al. (1998). The remaining possible infrared counterpart of KS 1731-260 (angular distance between sources ~1.45'', or ~2σ) has the brightness m_{J}~16 in the J band. If this star is really the counterpart of KS 1731-260, the lower limit on its luminosity is L_{tot}>L_{J,H}~10L_{\odot}. The strong drop of the X-ray flux from the source allow us to propose the additional check of whether the decribed star is the real counterpart of KS1731-260. If the optical and infrared brightness of the binary system is partially caused by the reprocessing of X-rays, as it is usual for the low mass binary systems, the infrared brightness of real counterpart should strongly reduce in 2001, when the X-ray flux from KS1731-260 turned off (Wijnands et al. 2001)