Hydra Observations of Aluminum Abundances in the Red Giants of the Globular Clusters M 80 and NGC 6752

Aluminum and other metal abundances were determined in 21 red giants in the globular clusters NGC 6752 and M80 as part of a larger study to determine whether the aluminum distribution on the red giant branch is related to the second parameter effect that causes clusters of similar metallicity to display different horizontal branch morphologies. The observations were obtained of the Al I lines near 6700 Å with the CTIO Blanco 4-m telescope and Hydra multi-object spectrograph. The spectra have a resolving power of 18000 or 9400, with typical S/N ratios of 100-200. Mean [Fe/H] values obtained from the spectra are –1.58 for NGC 6752 and –1.73 for M80; this represents the first spectroscopic iron abundance determination for M80. Both NGC 6752 and M80 display a spread in aluminum abundance, with mean [Al/Fe] ratios of +0.51 and +0.37, respectively. No trend in the variation of the mean Al abundance with position on the giant branch is discernible in either cluster with our small sample. Subject headings: globular clusters: individual (NGC 6752,M80) — stars: abundances — stars: horizontal branch — stars: late-type — stars: Population II Visiting Astronomer, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.