Lithium Evolution of Giant Stars Observed by LAMOST and Kepler
Lithium Evolution of Giant Stars Observed by LAMOST and Kepler
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DOI：
10.3847/2041-8213/ac224c
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发表时间：
2021-08
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通讯作者：
Jinghua Zhang;Jian-rong Shi;Hong-liang Yan;Yaguang Li;Q. Gao;Chun-qian Li;Xianfei Zhang;Shuai Liu;S. Bi;Gang Zhao;Yan Li
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作者：
Jinghua Zhang;Jian-rong Shi;Hong-liang Yan;Yaguang Li;Q. Gao;Chun-qian Li;Xianfei Zhang;Shuai Liu;S. Bi;Gang Zhao;Yan Li
绘制演化恒星的锂演化图将为基本的恒星内部物理过程提供约束和约束，这将进一步阐明我们对恒星结构和演化理论的理解。基于来自LAMOST-开普勒和LAMOST-K2场的1848颗已知演化阶段和锂丰度的巨星样本，我们构建了质量-半径图来刻画锂的演化特征。处于红巨星分支(RGB)相的恒星在恒星演化过程中表现为自然耗尽，特别是在凸起附近没有明显的群星具有异常高的Li丰度。大多数达到核心氦燃烧零龄序列的低质量恒星的Li丰度都在∼1.0dex附近，这表明Li丰度比∼凸起上方的恒星增加了0.6dex。这表明氦闪光可能是产生适中Li的原因，而对于超富Li星，在氦闪光过程中应考虑一些特殊的机制。其他情况，如合并，也可能是来源，因为在氦核心燃烧的稳定阶段，任何时候都可以发现富锂恒星。在堆芯烧氦(HEB)阶段，没有明显的锂耗竭迹象。
Mapping lithium evolution for evolved stars will provide restrictions and constraints on the fundamental stellar interior physical processes, which will shed further light on our understanding of the theory of stellar structure and evolution. Based on a sample of 1848 giants with known evolutionary phases and lithium abundances from the LAMOST-Kepler and LAMOST-K2 fields, we construct mass–radius diagrams to characterize the evolutionary features of lithium. The stars at red giant branch (RGB) phase show natural depletion along with their stellar evolution; particularly, there are no obvious crowd stars with anomalously high Li abundances near the bump. Most of the low-mass stars reaching their zero-age sequence of core helium burning (ZAHeB) have Li abundances around ∼1.0 dex, which shows an increase of Li abundance by ∼0.6 dex compared to the stars above the RGB bump. This suggests that helium flash may be responsible for moderate Li production, while for super Li-rich stars, some special mechanisms should be considered during helium flash. Other scenarios, such as mergers, could also be sources given that Li-rich stars can be found at any time during the steady-state phase of core He burning. During the core He-burning (HeB) phase, there is no indication of obvious lithium depletion.