Planets in Stellar Clusters Extensive Search. I. Discovery of 47 Low-Amplitude Variables in the Metal-rich Cluster NGC 6791 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. As ourfirst target we have chosen NGC 6791 -- a very old, populous, metal richcluster. In this paper we present the results of a test observing run at theFLWO 1.2 m telescope. Our primary goal is to demonstrate the feasibility ofobtaining the accuracy required for planetary transit detection using imagesubtraction photometry on data collected with a 1 m class telescope. We presenta catalog of 62 variable stars, 47 of them newly discovered, most with lowamplitude variability. Among those there are several BY Dra type variables. Wehave also observed outbursts in the cataclysmic variables B7 and B8 (Kaluzny etal. 1997).Comment: 15 pages LaTeX, including 8 PostScript figures and 3 tables. More discussion added on the implications for transit detection. Accepted for publication in the Astronomical Journal. Version with full resolution figures available through ftp at ftp://cfa-ftp.harvard.edu/pub/bmochejs/PISCES/papers/1_N6791