THE ASTRONOMICAL JOURNAL    VOLUME 110, NUMBER 5, PAGE 2206       NOVEMBER 1995

        CCD PHOTOMETRY OF VARIABLE STARS IN THE GLOBULAR CLUSTER RU 106

                                JANUSZ KALUZNY

   Warsaw University Observatory, Al. Ujazdowskie 4, 00-478, Warsaw, Poland
                  Electronic mail: jka@sirius.astrouw.edu.pl

                              WOJCIECH KRZEMINSKI

Carnegie Observatories, Las Campanas Observatory, Casilla 601, LaSerena, Chile
                  Electronic mail: wojtek@roses.ctio.noao.edu

                                  BEATA MAZUR

        Copernicus Astronomical Center, ul. Bartycka 18, Warsaw, Poland
                      Electronic mail: batka@camk.edu.pl


                                   ABSTRACT

    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] >= -1.6.