Metallicities on the Double Main Sequence of ω Centauri Imply Large Helium Enhancement
Metallicities on the Double Main Sequence of ω Centauri Imply Large Helium Enhancement
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DOI：
10.1086/427796
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发表时间：
2004-12
期刊：
影响因子：
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通讯作者：
G. Piotto;S. Villanova;L. Bedin;R. Gratton;S. Cassisi;Y. Momany;A. Recio-Blanco;S. Lucatello;
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文献类型：
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作者：
G. Piotto;S. Villanova;L. Bedin;R. Gratton;S. Cassisi;Y. Momany;A. Recio-Blanco;S. Lucatello;
在最近的一篇论文中已经表明，半人马座ω的主序列分为两个不同的分支，我们现在提出的光谱结果表明，蓝色序列的金属含量较低。我们仔细地结合VLT的GIRAFFE光谱的17颗恒星的每一个分裂到一个单一的光谱的每一个分支，有足够的信号噪声比，清楚地表明，恒星的蓝色主序列是少金属贫0.3德克斯比占主导地位的红色之一。通过对单个光谱的分析，我们无法检测到蓝色主序星之间的任何丰度分布，而红色主序星的金属丰度分布为0.2 dex。我们使用恒星结构模型表明，只有大大增强氦可以解释两个主要序列之间的颜色差异，我们讨论了这种增强可能出现的方式。
Having shown in a recent paper that the main sequence of ω Centauri is split into two distinct branches, we now present spectroscopic results showing that the bluer sequence is less metal-poor. We have carefully combined VLT's GIRAFFE spectra of 17 stars on each side of the split into a single spectrum for each branch, with adequate signal-to-noise ratio, to show clearly that the stars of the blue main sequence are less metal-poor by 0.3 dex than those of the dominant red one. From an analysis of the individual spectra, we could not detect any abundance spread among the blue main-sequence stars, whereas the red main-sequence stars show a 0.2 dex spread in metallicity. We use stellar structure models to show that only greatly enhanced helium can explain the color difference between the two main sequences, and we discuss ways in which this enhancement could have arisen.