Rapidly Rotating Lithium-rich K Giants: The New Case of the Giant PDS 365
Rapidly Rotating Lithium-rich K Giants: The New Case of the Giant PDS 365
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DOI：
10.1086/339968
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发表时间：
2002-02
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影响因子：
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通讯作者：
N. Drake;R. de la Reza;L. da Silva;D. Lambert
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作者：
N. Drake;R. de la Reza;L. da Silva;D. Lambert
PDS 365 是一颗新发现的快速旋转（v sin i = 20 km s-1）、单颗低质量巨星，它与 HD 233517 和 HD 219025 形成了一个引人注目的单 K 巨星星团，具有快速旋转、非常强的 Li 谱线、不对称的 Hα 剖面和大量远红外过剩的独特特性。它们的 v sin i 值在 18 到 23 km s-1 之间，并且它们的 LTE Li 丰度 log ε(Li) 在 2.9 到 3.9 之间。对 PDS 365 的详细分析表明它是一颗 ∼1 M⊙ 巨星，其 12C/13C 值约等于 12。只有当存在不对称 Hα 轮廓和大量远红外过量时，才能发现 K 巨星的高旋转速度和非常高的 Li 丰度之间的明确关系。如果我们考虑单个K巨星，我们发现在快速（v sin i ≥ 8 km s-1）旋转体中，很大一部分（∼50%）是富锂巨星。这一比例与更常见的缓慢旋转 K 巨星中非常低的富锂恒星比例 (∼2%) 形成鲜明对比。这种显着差异是根据所提出的锂富集机制进行讨论的。
PDS 365 is a newly detected, rapidly rotating (v sin i = 20 km s-1), single, low-mass giant star that with HD 233517 and HD 219025 forms a remarkable ensemble of single K giants with the unique properties of rapid rotation, very strong Li lines, an asymmetrical Hα profile, and a large far-infrared excess. Their v sin i values are between 18 and 23 km s-1, and their LTE Li abundances, log ε(Li), are between 2.9 and 3.9. Detailed analysis of PDS 365 reveals it to be a ∼1 M⊙ giant with a value of 12C/13C approximately equal to 12. A clear relation between high rotational velocities and very high Li abundances for K giant stars is found only when asymmetrical Hα profiles and large far-infrared excesses are present. If we consider single K giants, we find that among rapid (v sin i ≥ 8 km s-1) rotators, a very large proportion (∼50%) are Li-rich giants. This proportion is in contrast with a very low proportion (∼2%) of Li-rich stars among the much more common slowly rotating K giants. This striking difference is discussed in terms of proposed mechanisms for Li enrichment.