The nature of RXJ0052.1-7319

Abstract

The nature of the X-ray source RXJ0052.1-7319 is discussed from observational data obtained from ROSAT observations performed in 1995 and 1996. An accurate position is derived from ROSAT HRI observations performed in 1995. The 6" error circle contains two OGLE microlensing optical variables of which one has previously been identified with a 14.5 mag Be-type star in the Small Magellanic Cloud. During the October 1996 observation RXJ0052.1-7319 was found to be extremely bright (with a count rate of ~1.1+/-0.1 s^-1) and 15.3 second X-ray pulsations have been discovered during this observation. This indicates for a high-mass X-ray binary nature of the source. During the 1995 observation the X-ray source detected at the position of RXJ0052.1-7319 was a factor 200 fainter. The corresponding luminosity has changed from 5.2x10^37 erg s^-1 to 2.6x10^35 erg s^-1 assuming SMC membership of the source. It is unclear whether the so-far unidentified second optical variable contributes to the X-ray flux of the source.