Stellar Abundances in the Oldest Open Cluster: Berkeley 17

Abstract

As part of a program of abundance studies of old open clusters, we present an analysis of high-dispersion echelle spectra of three giant stars in the 10 Gyr old cluster Berkeley 17. Abundances were determined relative to the disk giant Arcturus. Be 17 is found to have a mean [Fe/H] = −0.10 ±0.05 (mean error). Oxygen abundances, determined from the forbidden [O I] lines, show solar abundance ratios. The α-elements Mg, Ca, and Ti also show scaled solar abundance ratios, with suggestions that the Si abundance is slightly enhanced. The odd-Z elements Na and Al are significantly enhanced relative to scaled solar abundances. These abundance patterns are similar to those in two other 8-10 Gyr old open clusters, Cr261 and NGC 6791, and suggest that the Galactic disk was enriched to solar abundance levels at very early times.