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快速旋转的大质量恒星在银河系膨胀中的印记
Cristina Chiappini1, Urs Frischknecht, Georges Meynet
1Astrophysikalisches Institut Potsdam, An der Sternwarte 16, Potsdam, 14482, Germany. cristina.chiappini@aip.de
Nature
|April 29, 2011
概括
第一颗恒星使宇宙充满了重元素. 对古代恒星的分析揭示了不寻常的元素丰度,这表明了早期恒星核合成的新模型,涉及快速旋转的大质量恒星.
科学领域:
- 天文学和天体物理学
- 恒星进化 恒星进化
- 太空化学 太空化学
背景情况:
- 早期的宇宙主要由和组成.
- 据理论,大质量恒星可以产生第一个重元素 ("金属").
- 球状星团包含一些最古老的恒星,保存了早期银河系的化学历史.
研究的目的:
- 研究古代球状星团NGC 6522中的恒星的化学组成.
- 解决大质量恒星预期的重元素丰度与古代恒星观察到的丰度之间的明显矛盾.
- 测试假设,金属贫乏,快速旋转的大质星可以解释观测到的元素模式.
主要方法:
- 重新分析了NGC 6522中八颗恒星的现有光谱数据.
- 详细分析了包括α元素,欧 (Eu), (Ba),兰坦 (La), (Y), (Sr) 和碳 (C) 在内的元素的丰度.
- 观测到的丰度与来自恒星核合成模型的预测进行比较.
主要成果:
- 在NGC 6522中的恒星显示高的α元素/Fe和Eu/Fe比率,与大质量恒星的丰富相一致.
- 这些恒星表现出异常高的Ba和La丰度相对于铁.
- 重新分析证实了Y和Sr的过剩,具有显著的分散,而碳丰度没有增加.
结论:
- 观测到的丰度模式,特别是高的Ba,La,Y和Sr,最好通过金属贫乏的快速旋转大质量恒星的核合成来解释.
- 这一发现支持了理论模型,这些模型增强了这些恒星中缓慢的中子捕获 (s过程) 元素的产生.
- 结果表明,金属贫困的快速旋转的大质星可能是早期宇宙中s过程元素的常见和重要来源,可能是第一个恒星世代的特征.
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