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Hydra observations of aluminum abundances in the red giants of the globular clusters M80 and NGC 6752
被引:28
作者:
Cavallo, RM
Suntzeff, NB
Pilachowski, CA
机构:
[1] Lawrence Livermore Natl Lab, Livermore, CA 94450 USA
[2] Natl Opt Astron Observ, Cerro Tololo Interamer Observ, La Serena, Chile
[3] Indiana Univ, Dept Astron, Bloomington, IN 47405 USA
关键词:
globular clusters : individual (NGC 6752;
M80);
stars : abundances;
stars : horizontal-branch;
stars : late-type;
stars : Population II;
D O I:
10.1086/421000
中图分类号:
P1 [天文学];
学科分类号:
0704 ;
摘要:
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 Angstrom with the Cerro Tololo Inter-American Observatory Blanco 4 m telescope and Hydra multiobject spectrograph. The spectra have a resolving power of 18,000 or 9400, with typical signal-to-noise 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.
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页码:3411 / 3421
页数:11
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