Lithium Enrichment-Mass-Loss Connection in K Giant Stars
Lithium Enrichment-Mass-Loss Connection in K Giant Stars
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DOI：
10.1086/309874
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发表时间：
1996-01
期刊：
影响因子：
--
通讯作者：
R. de la Reza;N. Drake;L. da Silva
中科院分区：
文献类型：
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作者：
R. de la Reza;N. Drake;L. da Silva
根据观测到的 K 巨星的远红外特性，我们提出了一种将其中一些恒星的高锂丰度与星周壳层演化联系起来的方案。在这个模型中，每一个质量在1.0到2.5 M☉之间的K巨星在红巨星分支阶段都会富锂，负责富锂的内部机制将启动一个迅速的质量损失事件。分离壳的演化路径与 2 km s-1 量级的低膨胀速度和 (2-5) × 10-8 M☉ yr-1 质量损失的观测结果相符。然而，这种适度的质量损失比正常的贫锂 K 巨星大 2 个数量级。 80,000 年或稍长的“Li 时间”是可能的。然而，这个Li相与12C/13C比率无关，对于这些低质量恒星来说，12C/13C比率似乎是在更长的时间内演化的。该模型需要快速的锂富集和耗尽的内部过程。讨论了文献中出现的有关这一内部过程的新论点。还提到了这些恒星对银河系李演化的重要性。
Based on observed far-infrared properties of K giant stars, we propose a scenario linking the high Li abundances of some of these stars to the evolution of circumstellar shells. In this model, every K giant with masses between 1.0 and 2.5 M☉ become Li rich during the red giant branch stage, and the internal mechanism responsible for the Li enrichment will initiate a prompt mass-loss event. The evolutionary paths of the detached shells are compatible with observations for low expansion velocities of the order of 2 km s-1 and mass loss of (2-5) × 10-8 M☉ yr-1. This modest mass loss is, however, 2 orders of magnitude larger than those of normal, Li-poor K giants. A “Li time” of the order of 80,000 yr or somewhat larger is possible. This Li phase is, nevertheless, not related to the 12C/13C ratio which appears to evolve, for these low-mass stars, over a much longer time. This model requires a rapid internal process of Li enrichment and depletion. New arguments appearing in the literature concerning this internal process are discussed. Reference is also made to the importance of these stars to the Galactic Li evolution.