Lithium in CEMP-no stars: A new constraint on the lithium depletion mechanism in the early universe
Lithium in CEMP-no stars: A new constraint on the lithium depletion mechanism in the early universe
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CEMP-无恒星中的锂：早期宇宙锂耗尽机制的新约束
DOI：
10.1093/pasj/psw129
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发表时间：
2016-12
期刊：
影响因子：
--
通讯作者：
Li H.N.
中科院分区：
文献类型：
--
作者：
Matsuno T.;Aoki W.;Suda T.;Li H.N.
大多数相对温暖、未演化的贫金属恒星（$T_{\rm eff}\gtrsim 5800\，\mathrm {K}$和$[{\rm Fe/H}]\lesssim-1. 5 $）表现出几乎恒定的锂丰度，与金属丰度或有效温度无关，因此形成所谓的Spite高原。这最初被解释为来自大爆炸核合成产生的锂。然而，最近的观测显示，超贫金属星（UMP星; $[\mathrm{Fe/H}]<-4.0$）的锂丰度明显低于高原。由于大多数UMP星是CEMP-无星，碳增强的贫金属星没有多余的中子捕获元素，碳增强和锂耗尽之间的联系被怀疑。这个问题的一个直接的方法是研究碳正常的UMP星。然而，在这个类中只有一个对象是已知的。作为一种替代方案，我们已经确定了两个CEMP-没有主序关闭恒星的锂丰度，金属丰度为$[{\rm Fe/H}]\sim-3. 0 $，其中有许多碳正常恒星可以考虑锂丰度。我们的一维LTE分析表明，这两颗CEMP-无恒星的锂丰度与平台附近的值一致，这表明碳增强和锂耗尽没有直接关系。相反，我们的研究结果表明，极低的铁丰度是UMP恒星中锂耗尽的根本原因。
Most of relatively warm, unevolved metal-poor stars ($T_{\rm eff}\gtrsim 5800\,\mathrm{K}$ and $[{\rm Fe/H}]\lesssim -1.5$) exhibit almost constant lithium abundances, irrespective of metallicity or effective temperature, and thus form the so-called Spite plateau. This was originally interpreted as arising from lithium created by the Big Bang nucleosynthesis. Recent observations, however, have revealed that ultra metal-poor stars (UMP stars; $[\mathrm{Fe/H}]<-4.0$) have significantly lower lithium abundances than that of the plateau. Since most of the UMP stars are CEMP-no stars, carbon-enhanced metal-poor stars with no excess of neutron-capture elements, a connection between the carbon enhancement and lithium depletion is suspected. A straightforward approach to this question is to investigate carbon-normal UMP stars. However only one object is known in this class. As an alternative, we have determined lithium abundances for two CEMP-no main-sequence turn-off stars with metallicities $[{\rm Fe/H}]\sim -3.0$, where there are numerous carbon-normal stars with available lithium abundances that can be considered. Our 1D LTE analysis indicates that the two CEMP-no stars have lithium abundances that are consistent with values near the plateau, which suggests that carbon enhancement and lithium depletion are not directly related. Instead, our results suggest that extremely low iron abundance is a fundamental cause to depleted lithium in UMP stars.
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DOI：
10.1086/338898
发表时间：
2002-03
期刊：
The Astronomical Journal
影响因子：
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作者：
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DOI：
10.1086/300289
发表时间：
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影响因子：
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DOI：
10.1051/0004-6361/201424153
发表时间：
2014-12
期刊：
arXiv: Solar and Stellar Astrophysics
影响因子：
--
作者：
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通讯作者：
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