Carbon-enhanced Metal-poor Stars: Osmium and Iridium Abundances in the Neutron-Capture-enhanced Subgiants CS 31062-050 and LP 625-44
Carbon-enhanced Metal-poor Stars: Osmium and Iridium Abundances in the Neutron-Capture-enhanced Subgiants CS 31062-050 and LP 625-44
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DOI：
10.1086/508878
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发表时间：
2006-09
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影响因子：
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通讯作者：
W. Aoki;S. Bisterzo;R. Gallino;T. Beers;J. Norris;S. Ryan;S. Tsangarides
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作者：
W. Aoki;S. Bisterzo;R. Gallino;T. Beers;J. Norris;S. Ryan;S. Tsangarides
我们研究了两个碳增强金属贫（CEMP）亚巨星CS 31062-050和LP 625-44中重中子捕获元素的丰度，包括锇（Os）和铱（Ir）。CS 31062-050被认为是一颗所谓的cmp -r/s星，它表现出大量过量的s过程元素，如钡（Ba）和铅（Pb），以及铕（Eu）的显著增强，这在渐近巨型分支星模型中无法用传统的s过程产生来解释。我们对该天体的高分辨率光谱分析首次确定了r过程核合成第三峰中Ir和Os元素的丰度。与标准s过程计算的预测相比，它们也表现出明显的过度。这两种元素在LP 625-44的相似质量光谱中未检测到；其丰度上限均低于cs31062 -050的丰度上限。我们比较了这两颗恒星中观测到的中子捕获元素（包括Os和Ir）的丰度模式与最近s过程的模型计算，并讨论了可能的解释。
We have investigated the abundances of heavy neutron-capture elements, including osmium (Os) and iridium (Ir), in the two carbon-enhanced metal-poor (CEMP) subgiants CS 31062-050 and LP 625-44. CS 31062-050 is known to be a so-called CEMP-r/s star, which exhibits large excesses of s-process elements such as barium (Ba) and lead (Pb), as well as a significant enhancement of europium (Eu) that cannot be explained by conventional s-process production in asymptotic giant branch star models. Our analysis of the high-resolution spectrum for this object has determined, for the first time, the abundances of Ir and Os, elements in the third peak of the r-process nucleosynthesis. They also exhibit significant excesses relative to the predictions of standard s-process calculations. These two elements are not detected in a similar quality spectrum of LP 625-44; the derived upper limits on their abundances are lower than the abundances in CS 31062-050. We compare the observed abundance patterns of neutron-capture elements, including Os and Ir, in these two stars with recent model calculations of the s-process, and we discuss possible interpretations.