Super lithium-rich K giant with low 12C to 13C ratio
Super lithium-rich K giant with low 12C to 13C ratio
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12C/13C比低的超级富锂K巨星
DOI：
10.1051/0004-6361/201730389
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发表时间：
2018-04
影响因子：
6.5
通讯作者：
Y. B. Kumar
中科院分区：
文献类型：
--
作者：
Y. T. Zhou;J. R. Shi;H. L. Yan;Q. Gao;J. B. Zhang;G. Zhao;K. Pan;Y. B. Kumar
上下文少数巨星的锂丰度超过了标准恒星演化模型的预测值，锂增强的机制仍在争论中。大天区多目标光纤光谱望远镜（LAMOST）在过去五年中获得了超过600万个光谱，因此为寻找这些稀有天体和更清楚地了解Li增强机制提供了很好的机会。
目标。本工作的目的是精确测量一颗新发现的超富锂巨星TYC 3251-581-1的Li丰度，并探讨其可能的Li富集机制。
方法.根据高分辨光谱，我们获得了恒星参数（Teff，logg，[Fe/H]），并确定了Li，C，N，α，Fe峰，r过程，s过程元素的丰度和投影自转速度。为了更好地理解混合过程的影响，我们还推导了12 C/13 C比值，并根据巴斯蒂恒星等时线约束了TYC 3251-581-1的演化状态。
结果超富锂巨星TYC 3251-581-1的A（Li）= 3.51，这是基于非局域热力学平衡分析的两条锂线在λ = 6708和6104处的平均丰度。大气参数表明目标位于光度函数凸点上。低的碳同位素比率（12 C scin 13 C = 9.0），缓慢的旋转速度vsini = 2.2 km s−1，并且没有IR过量的迹象，这表明在第一次挖掘（FDU）之后应该发生额外的混合，以将内部合成的Li带到表面。低碳（[C scinFe] ~-0.34）和高氮（[N scinFe] ~ 0.33）也与混合的迹象一致。
结论.考虑到TYC 3251-581-1所处的演化阶段和相对较低的12 C闪烁13 C，将Li包裹在外层的内部产生是该星星Li增强的最可能来源。
Context. The lithium abundances in a few percent of giants exceed the value predicted by the standard stellar evolution models, and the mechanisms of Li enhancement are still under debate. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey has obtained over six million spectra in the past five years, and thus provides a great opportunity to search these rare objects and to more clearly understand the mechanisms of Li enhancement.
Aims. The aim of this work is to accurately measure the Li abundance and investigate the possible mechanisms of Li enrichment for a newly found super Li-rich giant, TYC 3251-581-1, located near the luminosity function bump with a low carbon isotopic ratio.
Methods. Based on the high-resolution spectrum we obtained the stellar parameters (Teff, logg, [Fe/H]), and determined the elemental abundances of Li, C, N, α, Fe-peak, r-process, s-process elements, and the projected rotational velocity. For a better understanding of the effect of mixing processes, we also derived the 12C to 13C ratio, and constrained the evolutionary status of TYC 3251-581-1 based on the BaSTI stellar isochrones.
Results. The super Li-rich giant TYC 3251-581-1 has A(Li) = 3.51, the average abundance of two lithium lines at λ = 6708 Å and 6104 Å based on the non-local thermodynamic equilibrium analysis. The atmospheric parameters show that our target locates on the luminosity function bump. The low carbon isotopic ratio (12C∕13C = 9.0), a slow rotational velocity vsini = 2.2 km s−1, and no sign of IR excess suggest that additional mixing after first dredge up (FDU) should occur to bring internal synthesized Li to the surface. The low carbon ([C∕Fe] ~−0.34) and enhanced nitrogen ([N∕Fe] ~ 0.33) are also consistent with the sign of mixing.
Conclusions. Given the evolutionary stage of TYC 3251-581-1 with the relatively low 12C∕13C, the internal production which replenishes Li in the outer layer is the most likely origin of Li enhancement for this star.
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DOI：
10.1088/0004-637x/806/1/86
发表时间：
2015-04
期刊：
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影响因子：
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影响因子：
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2017-01
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DOI：
10.1086/339968
发表时间：
2002-02
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影响因子：
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