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.
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