We have conducted a deep ($15 \la r \la 23$), 20 night survey for transiting planets in the intermediate age ($\sim 550 { \rm Myr}$) open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5m Multiple Mirror Telescope (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 ($P < 1 { \rm day}$) pulsating stars. The bulk of the variables are most likely rapidly rotating young low-mass stars, including a substantial number ($\ga 500$) that are members of the cluster. We identify and analyze five particularly interesting individual variables including a previously identified variable which we suggest is probably a hybrid $\gamma$ Doradus/$\delta$ Scuti pulsator, two possible quiescent cataclysmic variables, a detached eclipsing binary (DEB) with at least one $\gamma$ Doradus pulsating component (only the second such variable found in an eclipsing binary), and a low mass ($M_{ P} \sim M_{ S} \sim 0.6 M_{ \odot}$) DEB that is a possible cluster member. A preliminary determination of the physical parameters for the DEB+$\gamma$ Doradus system yields $M_{ P} = 1.58 \pm 0.04 M_{ \odot}$, $M_{ S} = 1.58 \pm 0.04 M_{ \odot}$, $R_{ P} = 1.39 \pm 0.07 R_{ \odot}$ and $R_{ S} = 1.38 \pm 0.07 R_{ \odot}$.
Categories: astro-ph