DISCOVERY OF A PROBABLE CH STAR IN THE GLOBULAR-CLUSTER M14 AND IMPLICATIONS FOR THE EVOLUTION OF BINARIES IN CLUSTERS

We report the discovery of a probable CH star in the core of the Galac tic globular duster M14 (=NGC 6402 = C1735-032), identified from an in tegrated-light spectrum of the cluster obtained with the MOS spectrogr aph on the Canada-France-Hawaii telescope. From a high-resolution eche lle spectrum of the same star obtained with the Hydra fiber positioner and bench spectrograph on the WIYN telescope, we measure a radial vel ocity of -53.0 +/- 1.2 km s(-1). Although this velocity is inconsisten t with published estimates of the systemic radial velocity of M14 (e.g ., upsilon(r)(-) approximate to -123 km s(-1)), we use high-precision Hydra velocities for 20 stars in the central 2'.6 of M14 to calculate improved values for the cluster mean velocity and one-dimensional velo city dispersion: -59.5 +/- 1.9 km s(-1) and 8.2 +/- 1.4 km s(-1), resp ectively. Both the star's location near the tip of the red giant branc h in the cluster color-magnitude diagram and its radial velocity there fore argue for membership in M14. Since the intermediate-resolution MO S spectrum shows not only enhanced CH absorption but also strong Swan bands of C-2, M14 joins omega Cen as the only globular clusters known to contain ''classical'' CH stars. Although evidence for its duplicity must await additional radial velocity measurements, the CH star in M1 4 is probably, like all field CH stars, a spectroscopic binary with a degenerate (white dwarf) secondary. The candidate and confirmed CH sta rs in M14 and omega Cen, and in a number of Galactic dSph galaxies, ma y then owe their existence to the long timescales for the shrinking an d coalescence of hard binaries in low-concentration environments.