Planets in Stellar Clusters Extensive Search. IV. A Detection of a Possible Transiting Planet Candidate in the Open Cluster NGC 2158

We have undertaken a long-term project, Planets in Stellar Clusters ExtensiveSearch (PISCES), to search for transiting planets in open clusters. In thispaper we present the results for NGC 2158, an intermediate age, populouscluster. We have monitored the cluster for over 260 hours, spread over 59nights. We have detected one candidate transiting low luminosity object, witheclipse depth of 3.7% in the R-band. If the host star is a member of thecluster, the eclipse depth is consistent with a 1.7 R_J object. Clustermembership of the host is supported by its location on the cluster mainsequence (MS) and its close proximity to the cluster center (2'). We havediscovered two other stars exhibiting low-amplitude (4-5%) transits, V64 andV70, but they are most likely blends or field stars. Given the photometricprecision and temporal coverage of our observations, and current best estimatesfor the frequency and radii of short-period planets, the expected number ofdetectable transiting planets in our sample is 0.13. We have observed fouroutbursts for the candidate cataclysmic variable V57. We have discovered 40 newvariable stars in the cluster, bringing the total number of identifiedvariables to 97, and present for them high precision light curves, spanning 13months.Comment: 21 pages LaTeX, including 14 figures and 7 tables. To be published in the February 2006 Astronomical Journal. Paper with better resolution figures available at ftp://cfa-ftp.harvard.edu/pub/bmochejs/PISCES/papers/4_N2158/ms.ps.g