M67中子巨星揭示的锂和铍的相关贫化和稀释
Correlated Depletion and Dilution of Lithium and Beryllium Revealed by Subgiants in M 67
摘要：
锂（Li）和铍（Be）的表面含量提供了对恒星内部混合和循环机制的见解。老的疏散星团，M 67，在主序星和演化的恒星中，锂的丰度都得到了很好的研究。Be丰度给了我们一个更深层次的恒星探测器。我们已经采取了高分辨率的光谱与凯克我与HIRES确定Be丰度沿亚巨星分支的M 67，那里有戏剧性的亏损李。这些次巨星的质量范围从1.26到1.32 M $_{\odot}$，并且是从主序星演化而来的，这些主序星可能占据了在年轻星团中发现的锂-铍倾斜区域。Pace等人已经将M 67中103颗恒星的锂丰度调整到相同的尺度。质量更大的恒星$-$现在是从主序星$-$中最冷、演化最远的恒星，其锂含量在亚巨星分支中下降了400倍。我们的新Be丰度也显示出下降，但下降了$\sim$ 50倍。这两种元素一起下降，Li在这些次巨星中的下降比Li-Be倾斜星更陡峭。铍丰度相对于锂丰度的下降与希尔斯和德利扬尼斯的模型非常吻合，这是专门为M 67的次巨星而设计的。这些模型包括恒星自转引起的混合效应。这些M 67次巨星显示了主序的损耗和主序后Li和Be的稀释。
英文摘要：
The surface content of lithium (Li) and beryllium (Be) provide insights into the mixing and circulation mechanisms in stellar interiors. The old open cluster, M 67, has been well-studied for Li abundances in both main-sequence and evolved stars. The Be abundances give us a probe to a deeper level in stars. We have taken high-resolution spectra with Keck I with HIRES to determine Be abundances along the subgiant branch of M 67, where there are dramatic depletions of Li. These subgiants range in mass from 1.26 to 1.32 M$_{\odot}$ and have evolved from main-sequence stars that would have occupied the region of the Li-Be dip found in younger clusters. Lithium abundances have been adjusted to the same scale for 103 stars in M 67 by Pace et al. The more massive stars $-$ now the coolest and furthest-evolved from the main-sequence $-$ show a drop in Li by a factor of 400 across the subgiant branch. Our new Be abundances also show a decline, but by a factor of $\sim$50. The two elements decline together with Li showing a steeper decline in these subgiants than it does in the Li-Be dip stars. The relative decline in Be abundance compared to Li is remarkably well fit by the models of Sills & Deliyannis, made specifically for the subgiants in M 67. Those models include the effects of mixing induced by stellar rotation. These M 67 subgiants show the effects of both main-sequence depletion and post-main-sequence dilution of both Li and Be.
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