The frequency of carbon-enhanced metal-poor stars in the galaxy from the HERES sample

被引：166
作者：
Lucatello, Sara
Beers, Timothy C.
Christlieb, Norbert
Barklem, Paul S.
Rossi, Silvia
Marsteller, Brian
Sivarani, Thirupathi
Lee, Young Sun
机构：
[1] Osserv Astron Padova, I-35122 Padua, Italy
[2] Michigan State Univ, Ctr Study Cosm Evolut, Dept Phys & Astron, E Lansing, MI 48824 USA
[3] Michigan State Univ, Joint Inst Nucl Astrophys, E Lansing, MI 48824 USA
[4] Univ Hamburg, D-21029 Hamburg, Germany
[5] Uppsala Univ, Dept Astron & Space Sci, S-75120 Uppsala, Sweden
[6] Univ Sao Paulo, Dept Astron, Inst Astrom Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo, Brazil
来源：
ASTROPHYSICAL JOURNAL | 2006年 / 652卷 / 01期
基金：
巴西圣保罗研究基金会; 美国国家科学基金会;
关键词：
Galaxy : halo; stars : abundances; stars : carbon; stars : Population II;
D O I：
10.1086/509780
中图分类号：
P1 [天文学];
学科分类号：
0704 ;
摘要：
We estimate the frequency of carbon-enhanced metal-poor (CEMP) stars among very metal-poor stars, based on an analysis of 349 stars with available high-resolution spectra observed as part of the Hamburg/ESO R-process Enhanced Star (HERES) survey. We obtain that a lower limit of 21% +/- 2% of stars with [Fe/H] <= -2.0 exhibit [C/Fe] >= +1.0. These fractions are higher than those that have been reported by recent examinations of this question, based on substantially smaller samples of stars. We discuss the source of this difference and suggest that in order to take into account effects that result in a decrease of surface carbon abundance with advancing evolution, a definition of CEMP stars based on a [C/Fe] cutoff that varies as a function of luminosity is more appropriate. We discuss the likely occurrence of dilution and mixing for many CEMP stars, which, if properly accounted for, would increase this fraction still further.
引用
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页码：L37 / L40
页数：4
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