Low-mass stars in their core-helium-burning stage define the sharpest feature present in the color-magnitude diagrams of nearby galaxy systems: the red clump (RC). This feature has given rise to a series of methods aimed at measuring the distributions of stellar distances and extinctions, especially in the Magellanic Clouds and Milky Way Bulge. Because the RC is easily recognizable within the data of large spectroscopic and asteroseismic surveys, it is a useful probe of stellar densities, kinematics, and chemical abundances across the Milky Way disk; it can be applied up to larger distances than that allowed by dwarfs; and it has better accuracy than is possible with other kinds of giants. Here, we discuss the reasons for the RC narrowness in several sets of observational data, its fine structure, and the presence of systematic changes in the RC properties as regards age, metallicity, and the observed passband. These factors set the limits on the validity and accuracy of several RC methods defined in the ...

中文翻译：

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红丛星

处于核心氦燃烧阶段的低质量恒星定义了附近星系系统颜色-星等图中最清晰的特征：红团（RC）。这一特征催生了一系列旨在测量恒星距离和灭绝分布的方法，特别是在麦哲伦星云和银河系凸起中。由于 RC 在大型光谱和星震调查的数据中很容易识别，因此它是探索整个银河系盘面的恒星密度、运动学和化学丰度的有用探测器；它可以应用于比矮人允许的更远的距离；它比其他种类的巨人具有更好的准确性。在这里，我们讨论了几组观测数据中 RC 窄的原因，它的精细结构，RC 特性在年龄、金属丰度和观察到的通带方面存在系统变化。这些因素限制了...中定义的几种 RC 方法的有效性和准确性。