Deep MMT Transit Survey of the Open Cluster M37. II. Variable Stars

We have conducted a deep (15lesssim rlesssim 23), 20 night survey for transiting planets in the intermediate-age (~550 Myr) open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5 m MMT. In this paper we present a catalog and light curves for 1445 variable stars; 1430 (99%) of these are new discoveries. We have discovered 20 new eclipsing binaries and 31 new short-period (P < 1 day ) pulsating stars. The bulk of the variables are most likely rapidly rotating young low-mass stars, including a substantial number (gtrsim500) that are members of the cluster. We identify and analyze five particularly interesting individual variables, including a previously identified variable that we suggest is probably a hybrid γ Doradus/δ Scuti pulsator, two possible quiescent cataclysmic variables, a detached eclipsing binary (DEB) with at least one γ Doradus pulsating component (only the second such variable found in an eclipsing binary), and a low-mass (M_P ~ M_S ~ 0.6 M_⊙) DEB that is a possible cluster member. A preliminary determination of the physical parameters for the DEB+γ Doradus system yields M_P = 1.58 +/- 0.04 M_⊙, M_S = 1.58 +/- 0.04 M_⊙, R_P = 1.39 +/- 0.07 R_⊙, and R_S = 1.38 +/- 0.07 R_⊙.

Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.