ROSAT HRI catalogue of X-ray sources in the SMC region

Abstract

During the operational phase of the ROSAT satellite between 1990 and 1998 the X-ray telescope pointed 71 times to the Small Magellanic Cloud (SMC) for observations with the High Resolution Imager (HRI), covering a field of 5 deg x 5 deg. From this data a catalogue of 121 discrete X-ray sources was derived. By cross-correlating the source catalogue with the SIMBAD data base and the TYCHO catalogue, the systematic positional error of the HRI source positions could be reduced. In total the X-ray position for 99 HRI sources was corrected yielding positional errors between 1 arcsec and 16 arcsec. The HRI catalogue was also cross-correlated with the catalogues derived from the ROSAT Position Sensitive Propotional Counter (PSPC) pointings (Kahabka et al. 1999, Haberl et al. 2000). For 75 HRI sources PSPC counterparts were found and thus hardness ratios are given. With the help of the information obtained from the cross-correlations 56 HRI sources were identified with objects of known or proposed nature. Four foreground stars, six supernova remnants, four supersoft sources, 12 X-ray binaries, and one AGN were detected by the HRI. Based on the existence of a likely optical counterpart or properties like hardness ratio and X-ray to optical flux ratio, further 15 HRI sources were classified into different source types.