Variable Star Candidates in an Advanced Camera for Surveys Field of M31

Abstract

A search for variable stars is performed using two epochs of Hubble Space Telescope Advanced Camera for Surveys imaging data for a 9.28 arcmin² portion of M31. This data set reveals 254 sources that vary by at least 4 σ between epochs. The positions and two-epoch B-band (equivalent) photometry of these sources are presented. The photometry suggests that this catalog includes most of the RR Lyrae population of this portion of M31.