A variable star survey of the open cluster M37

A CCD photometric study of the dense galactic open cluster M37 is presented and discussed. The majority of the analysed data are time-series measurements obtained through an R_C filter. The observations were carried out on seven nights between December 1999 and February 2000, and have led to the discovery of 7 new variable stars in the field. Three of them have been unambiguously identified as W UMa-type eclipsing binaries, while two more are monoperiodic pulsating stars, most probably high-amplitude delta Scuti-type variables. The remaining two stars seem to be long-period eclipsing binaries without firm period determination. Johnson B and V frames have been used to construct a new colour-magnitude (CM) diagram of the cluster, and to find the locations of the new variable stars. The pulsating variables are most likely background objects. The CM diagram is fitted with recent isochrones yielding the main parameters of the cluster.