Elemental abundances and classification of carbon-enhanced metal-poor stars
Elemental abundances and classification of carbon-enhanced metal-poor stars
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DOI：
10.1051/0004-6361/201015615
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发表时间：
2012-10
影响因子：
6.5
通讯作者：
D. M. Allen;S. Ryan;S. Rossi;T. Beers;S. Tsangarides
中科院分区：
文献类型：
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作者：
D. M. Allen;S. Ryan;S. Rossi;T. Beers;S. Tsangarides
我们提出了一个详细的研究碳增强贫金属（CEMP）星，基于高分辨率光谱观测的样本的18颗恒星。该样本的恒星光谱是在2001年和2002年在4.2米威廉赫歇尔望远镜上获得的，使用乌得勒支埃歇尔摄谱仪，分辨率为R = 52000，信噪比为40，覆盖波长范围为λλ3700 - 5700 A。该样品的大气参数表明温度范围为4750 K至7100 K，log g为1.5至4.3，金属丰度为−3.0 ≤ [Fe/H] ≤− 1.7。测定了C、Na、Mg、Sc、Ti、Cr、Cu、Zn、Sr、Y、Zr、Ba、La、Ce、Nd、Sm、Eu、Gd、Dy的元素丰度。另外109颗恒星的丰度取自文献，并与我们样本的数据相结合。文献样本显示，缺乏可靠的丰度估计的物种，可能与r-过程元素的约67%的CEMP恒星，防止这类恒星的完整理解，因为[Ba/Eu]比被用来分类它们。虽然我们观察到的样品中的8颗星也发现在文献样品中，Eu丰度或限制确定为这些恒星的第一次。从观察到的C，Ba和Eu之间的相关性，我们认为，CEMP-r/s类具有相同的天文起源CEMP-s的恒星，突出需要一个更完整的了解Eu生产。
We present a detailed study of carbon-enhanced metal-poor (CEMP) stars, based on high-resolution spectroscopic observations of a sample of 18 stars. The stellar spectra for this sample were obtained at the 4.2 m William Herschel Telescope in 2001 and 2002, using the Utrecht Echelle Spectrograph, at a resolving power R ∼ 52 000 and S /N ∼ 40, covering the wavelength range λλ3700−5700 A. The atmospheric parameters determined for this sample indicate temperatures ranging from 4750 K to 7100 K, log g from 1.5 to 4.3, and metallicities −3.0 ≤ [Fe/H] ≤− 1.7. Elemental abundances for C, Na, Mg, Sc, Ti, Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, Gd, Dy are determined. Abundances for an additional 109 stars were taken from the literature and combined with the data of our sample. The literature sample reveals a lack of reliable abundance estimates for species that might be associated with the r-process elements for about 67% of CEMP stars, preventing a complete understanding of this class of stars, since [Ba/Eu] ratios are used to classify them. Although eight stars in our observed sample are also found in the literature sample, Eu abundances or limits are determined for four of these stars for the first time. From the observed correlations between C, Ba, and Eu, we argue that the CEMP-r/s class has the same astronomical origin as CEMP-s stars, highlighting the need for a more complete understanding of Eu production.