Planets in Stellar Clusters Extensive Search. II. Discovery of 57 Variables in the Cluster NGC 2158 with Millimagnitude Image Subtraction Photometry

We have undertaken a long-term project, Planets in Stellar Clusters ExtensiveSearch (PISCES), to search for transiting planets in open clusters. NGC 2158 isone of the targets we have chosen -- an intermediate age, populous, rathermetal poor cluster. In this paper we present the results of a search forvariable stars in the data from the first season of monitoring at the FLWO 1.2m telescope. This is the first variability search ever conducted in thiscluster. We present a catalog of 57 variable stars, most with low amplitudevariability. Among the variables is a cataclysmic variable (CV) which underwenta 2.5 mag outburst. If it is a member of NGC 2158, this would be the fourth CVknown in an open cluster. We have also found five delta Scuti stars, three ofwhich we have two or more detectable modes of pulsation. Of the 57 variablesdiscovered, 28 have R-band amplitudes of 5% or below. Six of those vary at orbelow the 2% level, including one with 0.08% variability.Comment: 13 pages LaTeX, including 8 figures and 4 tables, submitted to Astronomical Journal. Version with full resolution figures available through ftp at ftp://cfa-ftp.harvard.edu/pub/bmochejs/PISCES/papers/2_N2158