1999/04/19 by Judith G. Cohen, R. Gratton, Raffaele G. Gratton +3 · 5 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/307765
29 pages, 6 figures, accepted for publication in the ApJ
arxiv created 1999/04/19 · openalex publication_date 1999/10/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We provide a high-dispersion line-by-line abundance analysis of five red horizontal-branch (HB) stars in the extremely metal-rich Galactic globular cluster NGC 6553. These red HB stars are significantly hotter than the very cool stars near the tip of the giant branch in such a metal-rich globular cluster, and hence their spectra are much more amenable to an abundance analysis than would be the case for red giants. We find that the mean [Fe/H] for NGC 6553 is -0.16 dex, comparable to the mean abundance in the Galactic bulge found by McWilliam & Rich and considerably higher than that obtained from an analysis of two red giants in this cluster by Barbuy and coworkers. The relative abundance for the best-determined α-process element (Ca) indicates an excess of α-process elements of about a factor of 2. The metallicity of NGC 6553 reaches the average of the Galactic bulge and of the solar neighborhood.