发表机构
University of Chicago; NSF NOIRLab; University of North Texas; Universitat de Barcelona; Massachusetts Institute of Technology（芝加哥大学; 美国国家光学-红外天文研究实验室; 北德克萨斯大学; 巴塞罗那大学; 麻省理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过多波段测光、天体测量和高分辨率光谱确认了一颗CNO增强的超贫金属红巨分支星，其化学模式可由质量约21-28太阳质量的暗弱第三族超新星产额解释，并推测其形成于后来与银河系合并的超暗矮星系。
AI 中文摘要
我们报告了在$Gaia$任务的蓝光和红光光度计'XP'分光光度目录中独立识别出一颗超贫金属（UMP）恒星（$\rm[Fe/H] =-4.06$），其$Gaia$ DR3 $\texttt{source_id}$为4795913112968206720（GDR3_479591）。我们结合多波段测光、天体测量和高分辨率光谱，确认GDR3_479591是一颗位于距太阳约$6\\,{\rm kpc}$处的红巨分支（RGB）星。在局部热力学平衡下的丰度分析显示，相对于太阳水平，碳（$\rm[C/Fe] = +1.54$，经RGB耗尽的演化校正后）、氮（$\rm[N/Fe] = +2.64$）和氧（$\rm[O/Fe] = +2.62$）有显著增强。因此，CNO增强的GDR3_479591是仅有的5颗探测到氧丰度的UMP恒星之一。CNO过量伴随着其他几种轻元素（如Na、Mg、Al和Si）的增强。我们证明，GDR3_479591的化学模式可以由单颗第三族'暗弱'超新星的产额重现，其前身星质量约为21至28$\\,M_\odot$，爆炸能量较低（$0.3 \leq E_{\rm SN}/(10^{51}\\,{\rm erg}) \leq 0.9$）。此外，我们利用文献中的贫金属恒星表明，与近期对高红移星系的提议相反，[C/O]的轻度增强并不自动转化为银河系及其卫星星系中UMP恒星通常观测到的高[C/Fe]。GDR3_479591无法与银河系晕中任何最相关的吸积子结构在动力学上关联，我们推测它形成于一个后来与银河系合并的超暗矮星系环境中。
英文摘要
We report an independent identification of the ultra metal-poor (UMP) star ($\rm[Fe/H] =-4.06$) $Gaia$ DR3 $\texttt{source_id}$ 4795913112968206720 (GDR3_479591) in the $Gaia$ mission's Blue and Red Photometer 'XP' spectro-photometric catalog. We combine multi-band photometry, astrometry, and high-resolution spectroscopy to confirm GDR3_479591 as a red giant-branch (RGB) star located at ${\sim} 6\,{\rm kpc}$ from the Sun. Abundance analysis under local thermodynamic equilibrium reveals significant enhancements, relative to the solar level, in carbon ($\rm[C/Fe] = +1.54$, after evolutionary correction for depletion in the RGB), nitrogen ($\rm[N/Fe] = +2.64$), and oxygen ($\rm[O/Fe] = +2.62$). The CNO-enhanced GDR3_479591 is thus one of only 5 UMP stars with a detected oxygen abundance. The CNO excess is accompanied by enhancements in several other light elements, such as Na, Mg, Al, and Si. We demonstrate that the chemical pattern of GDR3_479591 can be reproduced by the yields of a single Population~III 'faint' supernova with progenitor mass of $\sim$21-to-28$\,M_\odot$ and a low explosion energy of ($0.3 \leq E_{\rm SN}/(10^{51}\,{\rm erg}) \leq 0.9$). Additionally, we use literature metal-poor stars to show that, contrary to recent propositions for high-redshift galaxies, a mild enhancement in [C/O] does not automatically translate to the high [C/Fe] typically observed in UMP stars in the Milky Way and its satellites. GDR3_479591 could not be dynamically associated with any of the most relevant accreted substructures in the Galactic halo, and we speculate that it was formed in an ultra-faint dwarf galaxy environment that later merged with the Milky Way.
CommentsSubmitted to AAS journals. Comments are appreciated and warmly welcomed!
