Discovery of New RR Lyrae Stars in the Center of the Globular Cluster M53

Abstract

We report the discovery of 17 new RR Lyrae variables in the central region (r≤1’) of the globular cluster M53. There candidates were identified by using the Welch & Stetson (1993) technique and confirmed by checking individual light curves in both B and V bands. The color-magnitude diagram of the horizontal-branch stars in the central region is compared with that for stars observed in the outer region by Rey et al. (1998). Including the new data from this study, we estimate the fraction of c typeRR Lyrae variables, n(c)/n(ab + c), to be 0.43 which agrees well with the valuse of other Oosterhoff group II clusters.