THE METAL ABUNDANCE AND AGE OF THE GLOBULAR-CLUSTER RUPRECHT 106

Spectra have been obtained at the Ca II triplet of nine stars in the field of the globular cluster Ruprecht 106, a cluster which Buonanno et al [AJ, 100, 1811 (1990)] have recently suggested is both metal poor and younger by 4-5 Gyr than other metal-poor globular clusters such as NGC 6397 and NGC 4590 (M68). Seven of the stars observed are cluster members and when compared with similar spectra of stars in NGC 4590, NGC 6397, NGC 6752, and M4, their line strengths yield an abundance for Ruprecht 106 of [Fe/H] = - 1.69 +/- 0.05 dex, a value more metal rich than that suggested by Buonanno et al With our abundance, analysis of a color-magnitude diagram based on NTT data [Buonanno et al, ASP Conf. Ser., Vol. 13, p. 240 (1991)] indicates that Ruprecht 106 is approximately 3 Gyr younger than NGC 6752, a cluster with similar abundance but possessing a blue horizontal branch. Since Ruprecht 106 has a red horizontal branch, this result suggests that age does play a role in the solution of the "second parameter problem" for globular cluster horizontal-branch morphology. The Ruprecht 106 spectra also yield a heliocentric radial velocity for the cluster of -44 +/- 3 km/s. Following the precepts of Armandroff [AJ, 97, 375 (1989)], this velocity, together with the cluster's location, allows an unambiguous classification of Ruprecht 106 as kinematically a halo object.