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Multiple Stellar Populations in Globular Clusters
Annual Review of Astronomy and Astrophysics ( IF 33.3 ) Pub Date : 2018-09-14 , DOI: 10.1146/annurev-astro-081817-051839
Nate Bastian 1 , Carmela Lardo 1, 2
Affiliation  

Globular Clusters (GCs) exhibit star-to-star variations in specific elements (e.g., He, C, N, O, Na, Al) that bare the hallmark of high temperature H burning. These abundance variations can be observed spectroscopically and also photometrically, with the appropriate choice of filters, due to the changing of spectral features within the band pass. This phenomenon is observed in nearly all of the ancient GCs, although, to date, has not been found in any massive cluster younger than 2~Gyr. Many scenarios have been suggested to explain this phenomenon, with most invoking multiple epochs of star-formation within the cluster, however all have failed to reproduce various key observations, in particular when a global view of the GC population is taken. We review the state of current observations, and outline the successes and failures of each of the main proposed models. The traditional idea of using the stellar ejecta from a 1st generation of stars to form a 2nd generation of stars, while conceptually straight forward, has failed to reproduce an increasing number of observational constraints. We conclude that the puzzle of multiple populations remains unsolved, hence alternative theories are needed.

中文翻译:

球状星团中的多个恒星种群

球状星团 (GC) 在特定元素(例如 He、C、N、O、Na、Al)中表现出星间变化,这些元素暴露了高温 H 燃烧的特征。由于带通内光谱特征的变化,这些丰度变化可以通过光谱和光度计观察到,选择适当的滤光片。这种现象在几乎所有的古代 GC 中都可以观察到,尽管迄今为止还没有在任何小于 2~Gyr 的大质量星团中发现。已经提出了许多方案来解释这种现象,其中大多数是在星团内调用了多个恒星形成时期,但是都未能重现各种关键观察结果,尤其是在采用全球范围内的 GC 群体视图时。我们回顾了当前观察的状态,并概述每个主要提议模型的成功和失败。使用第一代恒星的恒星喷射物形成第二代恒星的传统想法虽然在概念上很简单,但未能重现越来越多的观测约束。我们得出结论,多个种群的难题仍未解决,因此需要替代理论。
更新日期:2018-09-14
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