J0023 +0307：来自SDSS/BOSS的一颗巨贫金属矮星
J0023+0307: A mega metal-poor dwarf star from SDSS/BOSS
摘要：
只有少数恒星的铁丰度[Fe/H]<-5，只有一颗[Fe/H]<-7。这些恒星有非常大的碳铁比，A（C）~7.0，很可能是由于核心坍缩超新星的回落，这使得它们的总金属丰度Z远高于铁丰度。在理论模型的支持下，未能找到第三星族星（即没有金属的星族星）被解释为头重脚轻的初始质量函数的结果。在金属丰度为零或非常低的情况下，限制辐射冷却，可以抑制低质量恒星的形成。目前，恒星SDSS J1029+1729将低质量恒星形成的潜在金属丰度阈值设定为log Z/Z_0~-5。SDSS J 0023 +0307是一颗原始星，T_eff =6188 ± 84 K，log g=4.9 ± 0.5，上限[Fe/H]<-6.6，碳丰度A（C）< 6.3。在我们寻求降低金属丰度阈值的过程中，我们发现J 0023 +0307是已知的两颗最缺铁的恒星之一，它的碳含量比大多数[Fe/H]<-5的恒星都要少。
英文摘要：
Only a handful of stars have been identified with an iron abundance [Fe/H]<-5, and only one at [Fe/H]<-7. These stars have very large carbon-to-iron ratios, with A(C)~7.0, most likely due to fallback in core-collapse supernovae, which makes their total metallicity Z much higher than their iron abundances. The failure to find population III stars, those with no metals, has been interpreted, with support from theoretical modeling, as the result of a top-heavy initial mass function. With zero or very low metal abundance limiting radiative cooling, the formation of low-mass stars could be inhibited. Currently, the star SDSS J1029+1729 sets the potential metallicity threshold for the formation of low-mass stars at log Z/Z_0~-5. We have identified SDSS J0023+0307, a primitive star with T_eff =6188+-84 K, and log g=4.9+-0.5, an upper limit [Fe/H]< -6.6, and a carbon abundance A(C)< 6.3. In our quest to push down the metallicity threshold we find J0023+0307 to be one of the two most iron-poor stars known, and it exhibits less carbon that most of stars at [Fe/H]< -5.
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