Optical identification of the LMC supersoft source RXJ0527.8-6954 from MACHO Project photometry

Abstract

We identify the likely optical counterpart to the LMC supersoft X-ray source RXJ0527.8-6954, and hence recover HV2554. This identification is based on an analysis of approximately 4 years of optical photometry obtained serendipitously via the MACHO project. We see a steady fading of the star of about 0.5 mag over the duration of the observations. Evidence is also presented for an orbital modulation of 0.05 mag semi-amplitude on a period of P=0.39262 +/- 00015 d. Our optical observations are consistent with the suggestion that the X-ray decline in this system is caused by cooling after a weak shell flash.