CCD PHOTOMETRY OF VARIABLE-STARS IN THE GLOBULAR-CLUSTER RU-106

BV photometry is presented for 12 RR Lyr variables discovered in the presumably young galactic globular cluster Ruprecht 106. All variables are type RRab, and their periods span a narrow range from 0.574 to 0.652 day. We report also on the discovery of three SX Phe variables among the cluster blue stragglers. A Likely background RR Lyr variable and two foreground contact binaries were also found in the cluster field. The reddening of Ruprecht 106 is estimated at E(B-V)=0.20 based on the (B-V) colors exhibited by the cluster RR Lyr variables at minimum Light. Analysis of the period vs amplitude and period vs rise-time diagrams suggests similar metallicities of Ruprecht 106 and M3. A peak (or bump) is present in the luminosity function of the red giant branch of Ru 106. Its position relative to the horizontal branch is consistent with a cluster metallicity of [Fe/H]greater than or equal to-1.6. (C) 1995 American Astronomical Society.