THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES 90:83-113, 1994 January

             A SEARCH FOR BINARIES IN THE GLOBULAR CLUSTER NGC 3201

            PATRICK COTE, DOUGLAS L. WELCH, AND PHILIPPE FISCHER
           Department of Physics and Astronomy, McMaster University,
                         Hamilton, ON, Canada L8S 4M1

                                G. S. DA COSTA
    Anglo-Australian Observatory, P.O. Box 296, Epping, NSW 2121, Australia

                                 PETER TAMBLYN
         Steward Observatory, University of Arizona, Tucson, AZ, 85721

                                PATRICK SEITZER
     Department of Astronomy, University of Michigan, Ann Arbor, MI, 48109

                                      AND

                                  M. J. IRWIN
      Royal Greenwich Observatory, Madingley Road, Cambridge, CB3 0HA, UK


                                   ABSTRACT

      We present BV CCD and APM photometry, accurate astrometry and 1859
    radial velocities for 1318 stars within ~36 deg of the Galactic
    globular cluster NGC 3201.  The field and cluster populations separate
    unambiguously in two distinct samples since the systemic radial
    velocity of NGC 3201 is 494.2 km/s.  After removal of the 19 known NGC
    3201 photometric variables in our sample, we have a database of 930
    radial velocities for 420 member giants (276 of which have multiple
    velocity measurements) with which to identify spectroscopic binaries on
    the basis of radial velocity variations.  The mean time span of the
    observations is 1.7 yr, with coverage up to ~6 yr for our best-studied
    stars.  Monte Carlo simulations of the observed velocity variations
    have provided _upper_limits_ to the cluster binary fraction (for
    binaries with 0.1 <= P <= 5-10 yr and mass ratios in the range 0.1-1)
    of 0.06-0.10 (circular orbits) and 0.15-0.18 (eccentric orbits).  These
    results suggest an incidence of binarism for NGC 3201 consistent with
    the corresponding incidence among nearby solar-type stars having
    similar periods and mass ratios (0.04-0.08) and that for a small sample
    of other globular clusters (0.05-0.12) studied by Hut et al. (1992).

    Subject headings: astrometry -- binaries: general -- globular clusters:
                      individual (NGC 3201) -- techniques: radial velocities