Short Period Variable Stars in Globular Cluster M71
Session 50 -- Globular Clusters
Display presentation, Wednesday, 9:20-6:30, Pauley Room

## [50.02] Short Period Variable Stars in Globular Cluster M71

Lin Yan (Caltech), Mario Mateo (Carnegie Observatories)

Based on the analysis of multi-epoch CCD images, we report the discovery of 6 short period variables in the field of the metal-rich low concentration globular cluster M71. The observations were taken with $1024\times 1024$ CCD (which offers $6.3\times 6.3$ square arcminutes field of view) at the $60''$ telescope of Palomar observatory during June and August 1991. Of the 6 newly discovered binary candidates, four stars are definitely eclipsing binaries and two need more data to determine their true nature. From the light curves of these four eclipsing systems, we found that one is a RS CVn type semidetached or fully detached binary with the period of 0.31 days, while the other three are W UMa type contact binaries with periods of 0.35 days, 0.37 days and 0.56 days respectively. Of the six variables, the one with 0.37 day period, which is 2 magnitudes below the main sequence turnoff, is about 0.3 magnitude redder than the main sequence line, which suggests that it is a field star. The six variables show no central concentration in the cluster. However, the further interpretation of this result requires better understanding of the cluster membership of these six candidates.