An abundance analysis for five red horizontal-branch stars in the extremely metal-rich globular cluster NGC 6553

被引:90
作者
Cohen, JG
Gratton, RG
Behr, BB
Carretta, E
机构
[1] CALTECH, Palomar Observ, Pasadena, CA 91125 USA
[2] Osservatorio Astron Padova, I-35122 Padua, Italy
关键词
globular clusters : individual (NGC 6553); stars : abundances; stars : horizontal-branch;
D O I
10.1086/307765
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We provide a high-dispersion line-by-line abundance analysis of five red horizontal-branch (HB) stars in the extremely metal-rich Galactic globular duster NGC 6553. These red HE 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 alpha-process element (Ca) indicates an excess of alpha-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.
引用
收藏
页码:739 / 751
页数:13
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