标题： 红巨星分支阶段转变：对RGB亮度函数隆起及富锂红团簇星的探测的影响 显示英文标题

标题： The red giant branch phase transition: Implications for the RGB luminosity function bump and detections of Li-rich red clump stars

摘要： 我们详细研究了不同金属丰度下红巨星分支演化阶段氦点启燃亮度以及红巨星分支膨胀点亮度的变化。为此，我们计算了一组恒星模型网格，这些模型以步长为${\rm 0.01M_\odot}$的精细质量间隔采样了过渡区域的质量范围。我们发现，对于具有特定初始化学成分的恒星群体，在大约 1.1-1.2 Gyr 的临界年龄附近，仅仅减少 20-30 百万年的年龄就会导致红巨星分支顶端亮度急剧下降。我们还发现，在过渡区域附近存在一个狭窄的年龄范围（几$10^7$年），在此范围内红巨星分支膨胀点的亮度比氦点启燃的亮度更高。我们讨论了这一现象与锂富集的核心氦燃烧星观测结果之间可能存在的联系。 显示英文摘要

摘要： We performed a detailed study of the evolution of the luminosity of He-ignition stage and of the red giant branch bump luminosity during the red giant branch phase transition for various metallicities. To this purpose we calculated a grid of stellar models that sample the mass range of the transition with a fine mass step equal to ${\rm 0.01M_\odot}$. We find that for a stellar population with a given initial chemical composition, there is a critical age (of 1.1-1.2~Gyr) around which a decrease in age of just 20-30 million years causes a drastic drop in the red giant branch tip brightness. We also find a narrow age range (a few $10^7$ yr) around the transition, characterized by the luminosity of the red giant branch bump being brighter than the luminosity of He ignition. We discuss a possible link between this occurrence and observations of Li-rich core He-burning stars.