A New Type of Extremely Metal-poor Star
A New Type of Extremely Metal-poor Star
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DOI：
10.1086/518031
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发表时间：
2007-03
期刊：
影响因子：
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通讯作者：
J. Cohen;A. McWilliam;N. Christlieb;S. Shectman;I. Thompson;J. Meléndez;L. Wisotzki;D. Reimers
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文献类型：
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作者：
J. Cohen;A. McWilliam;N. Christlieb;S. Shectman;I. Thompson;J. Meléndez;L. Wisotzki;D. Reimers
我们提出了一种基于Keck的高色散光谱的极贫金属（EMP）恒星HE 1424-0241的丰度分析。这颗恒星是红巨星分支下部的一颗巨星，指数为[Fe/H] ~ -4.0。相对于Fe， HE 1424-0241有正常的Mg，但它显示出非常大的Si缺陷，其柱(Si)/柱（Fe） ~ 1/10和柱(Si)/柱（Mg） ~ 1/25是所有已知的EMP巨星或矮星的。在HE 1424-0241中，我们看到了非常少量的贡献超新星的影响，而贡献HE 1424-0241化学库存的SNe II在前体质量或爆炸特性上存在偏差，从而重现了其异常的极低的Si/Mg比值。HE 1424-0241缺乏爆炸α-燃烧元素Si、Ca和Ti，并伴有EMP恒星正常的Mg/Fe比值；Mg通过流体静压α-燃烧产生。最新的SNe II核合成模型无法重现在HE 1424-0241中看到的丰度比，无论它们探索的核心坍缩爆炸参数空间的任何组合。
We present an abundance analysis for the extremely metal-poor (EMP) star HE 1424-0241 based on high-dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ~ -4.0 dex. Relative to Fe, HE 1424-0241 has normal Mg, but it shows a very large deficiency of Si, with ϵ(Si)/ϵ(Fe) ~ 1/10 and ϵ(Si)/ϵ(Mg) ~ 1/25 that of all previously known EMP giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE 1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNe II contributing to the chemical inventory of HE 1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE 1424-0241 shows a deficiency of the explosive α-burning elements Si, Ca, and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic α-burning. The latest models of nucleosynthesis in SNe II fail to reproduce the abundance ratios seen in HE 1424-0241 for any combination of the parameter space of core-collapse explosions they explore.