THE ASTRONOMICAL JOURNAL    VOLUME 109, NUMBER 3, PAGE 1112          MARCH 1995

           CCD PHOTOMETRY FOR THE GALACTIC GLOBULAR CLUSTER NGC 6584

                                ATA SARAJEDINI

   Kitt Peak National Observatory, National Optical Astronomy Observatories,
                     P.O. Box 26732, Tucson, Arizona 85726
                         Electronic mail: ata@noao.edu

                              WENDY L. FORRESTER

              8215 N. Oracle Rd., Apt. #45, Tucson, Arizona 85704


                                   ABSTRACT

    We present CCD photometry in the B and V passbands for the Galactic
    globular cluster NGC 6584.  The color-magnitude diagram reveals a
    horizontal branch (HB) populated on both the red and blue sides of the
    RR Lyrae instability strip. The cluster contains 42 confirmed RR Lyrae
    variables, and we find an additional 56 stars which are possible RR
    Lyraes.  The mean magnitude of the RR Lyraes on our CCD frames is
    combined with that of the nonvariable stars to yield <V(HB)> = 16.53
    +/- 0.03.  Using a polynomial fit to the cluster giant stars, we derive
    the color of the giant branch at the level of the HB to be (B-V)g =
    0.89 +/- 0.02.  Our photometry has also been used to isolate the red
    giant branch "clump," which forms when stars pause and sometimes
    reverse their course as they evolve up the giant branch.  Its
    luminosity is primarily dependent upon the cluster metallicity, and we
    have used this fact to derive a metallicity of [Fe/H] = -1.44 +/- 0.16
    for NGC 6584.  Coupled with the color of the giant branch given above,
    this yields a cluster reddening of E(B-V) = 0.07 +/- 0.04.  To the
    extent that our photometry can be used to study the age of NGC 6584, we
    find it to be comparable to M3, which is not surprising given their
    similar HB morphologies.  The color-magnitude diagram also exhibits a
    significant population of blue straggler stars.  From a comparison of
    the blue straggler radial distribution to that of the subgiant stars
    with similar V magnitudes, we find that the blue stragglers are more
    centrally concentrated than the subgiants, indicative of a higher mass
    for the blue stragglers.