旧恒星中的原子扩散和混合 - - VIII. 球状星团M4 (NGC 6121) 中的化学丰度变化
T Nordlander1,2,3, P Gruyters3,4, O Richard5
1Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia.
Monthly notices of the Royal Astronomical Society
|January 15, 2024
概括
球状星团NGC 6121 (M4) 中恒星的化学丰度变化与包含原子扩散和额外混合的模型保持一致. 这些发现揭示了对古代恒星群体的恒星进化和核合成的见解.
科学领域:
- 天文学和天体物理学
- 恒星进化 恒星进化
- 银河系考古学 银河系考古学
背景情况:
- 在球状星团和开放星团内的恒星中观察到化学丰度的变化.
- 这些变化受到恒星金属性和进化阶段的影响.
- 原子扩散和额外的混合过程是恒星化学进化的关键因素.
研究的目的:
- 为了研究银河系球状星团NGC 6121 (M4) 中的化学丰度变化.
- 分析原子扩散和额外混合对恒星化学丰度的影响.
- 研究第二代恒星的组成及其污染源.
主要方法:
- 在NGC 6121中使用ESO VLT FLAMES高分辨率光谱仪对86颗恒星进行了详细的化学丰度分析.
- 从主顺序的转折点 (TOP) 到红色巨星分支 (RGB) 检查恒星.
- 将观察到的丰度变化与来自恒星结构和进化模型的预测进行比较.
主要成果:
- 确定了碳--氧 (C-N-O) 和-- (Mg-Al-Si) 的丰度反相关性.
- 确认了一个双模群体,丰度差异为1dex.
- 在TOP和RGB恒星之间观察到化学丰度的进化变化,与高效的额外混合相一致.
结论:
- 第二代恒星的化学组成表明,来自大质量恒星和非对称巨型分支恒星的污染.
- 观察到的丰度变化很弱,但当包括有效的额外混合时,与模型预测相匹配.
- 导出了2.63±0.10的初始丰度,略低于原始大爆炸核合成值.
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