Metal abundances of RR Lyrae stars in the metal-rich globular cluster NGC 6441

被引:31
作者
Clementini, G [1 ]
Gratton, RG
Bragaglia, A
Ripepi, V
Fiorenzano, AFM
Held, EV
Carretta, E
机构
[1] Osservatorio Astron Bologna, INAF, I-40127 Bologna, Italy
[2] Astron Observ Padova, INAF, I-35122 Padua, Italy
[3] Osserv Astron Capodimonte, INAF, I-80131 Naples, Italy
[4] Univ Padua, Dipartimento Astron, I-35122 Padua, Italy
关键词
globular clusters : individual (NGC 6441); stars : abundances; stars : horizontal-branch stars : variables : other; techniques : spectroscopic;
D O I
10.1086/491789
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Low- resolution spectra have been used to measure individual metal abundances of RR Lyrae stars in NGC 6441, a Galactic globular cluster known to have very unusual horizontal- branch morphology and periods of the RR Lyrae stars for its high metallicity. We find an average metal abundance of ( dex) [ Fe/ H] p -0.69 +/- 0.06 rms p 0.33 and ( dex) on Zinn & West and Carretta & Gratton metallicity scales, re- [ Fe/ H] p - 0.41 +/- 0.06 rms p 0.36 spectively, consistent with the cluster metal abundance derived by Armandroff & Zinn. Most of the metallicities were extrapolated from calibration relations defined for; however, they are clearly high and contrast [ Fe/ H] <= -1 with the rather long periods of the NGC 6441 variables, thus confirming that the cluster does not fit in the general Oosterhoff classification scheme. The rms scatter of the average is larger than observational errors ( 0.15 - 0.16 dex), possibly indicating some spread in metallicity. However, even the metal- poor variables, if confirmed to be cluster members, are still more metal- rich than those commonly found in the Oosterhoff type II globular clusters.
引用
收藏
页码:L145 / L148
页数:4
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