Variable stars in the field of the old open cluster NGC 2243

Abstract

We report results of photometric monitoring of the NGC 2243 field in V and $I$ filters. Two W~UMa-type systems and three detached eclipsing binaries were discovered. Both contact systems are likely members of the cluster. One of detached binaries - variable V1 - has a period P=1.188 day. This variable is located at the cluster's turnoff in the color-magnitude diagram. Determination of parameters for components of V1 can provide direct information about properties of turnoff stars in NGC 2243 as well as to allow direct determination of cluster's distance. A background RR Lyr variable was found in the monitored field. The reddening of NGC 2243 is estimated at E(V-I)=0.10\pm 0.04 based on the V-I color exhibited by this star at minimum light. The observed distribution of colors for the background halo stars shows a cutoff at (V-I)\approx 0.60 what implies $E(V-I)\leq 0.12$ for the cluster.