标题： 恒星模型在低金属丰度下是可靠的：KIC 8144907这颗古老且极低金属丰度恒星的星震学年龄 显示英文标题

标题： Stellar Models are Reliable at Low Metallicity: An Asteroseismic Age for the Ancient Very Metal-Poor Star KIC 8144907

摘要： 极贫金属星（[Fe/H] < -2）是检验恒星模型和重建银河系形成历史的重要实验室。 星震学是一种探测恒星内部结构和测量年龄的强大工具，但在极贫金属星中仅有少数几个星震学探测被发现，且没有一个能够允许详细的振荡频率建模。 我们报告了开普勒红巨星（KIC 8144907）的发现，该星具有高信噪比的振荡现象，[Fe/H]=-2.66±0.08 和 [α/Fe]=0.38±0.06，使其成为迄今为止最有可能进行详细星震学建模的极贫金属星。 通过结合开普勒振荡光谱与高分辨率光谱，我们测得其星震学质量和年龄分别为： 0.79±0.02（随机）±0.01（系统）太阳质量 和 12.0±0.6（随机）±0.4（系统）十亿年，不同代码和输入物理之间的结果高度一致，表明当使用单独的频率时，恒星模型和星震学对于极贫金属星是可靠的。 这些结果还为银河系早期形成提供了直接的年龄基准，暗示大规模恒星形成直到红移 z~3 才开始（如果该星是在本地形成的），或者银河系至少经历了 ~12 十亿年的合并事件（如果该星是由矮卫星星系合并（如盖亚恩刻拉多斯）吸积而来）。 显示英文摘要

摘要： Very metal-poor stars ([Fe/H]<-2) are important laboratories for testing stellar models and reconstructing the formation history of our galaxy. Asteroseismology is a powerful tool to probe stellar interiors and measure ages, but few asteroseismic detections are known in very metal-poor stars and none have allowed detailed modeling of oscillation frequencies. We report the discovery of a low-luminosity Kepler red giant (KIC 8144907) with high S/N oscillations, [Fe/H]=-2.66+/-0.08 and [alpha/Fe]=0.38+/-0.06, making it by far the most metal-poor star to date for which detailed asteroseismic modeling is possible. By combining the oscillation spectrum from Kepler with high-resolution spectroscopy we measure an asteroseismic mass and age of 0.79+/-0.02(ran)+/-0.01(sys) Msun and 12.0+/-0.6(ran)+/-0.4(sys) Gyr, with remarkable agreement across different codes and input physics, demonstrating that stellar models and asteroseismology are reliable for very metal-poor stars when individual frequencies are used. The results also provide a direct age anchor for the early formation of the Milky Way, implying that substantial star formation did not commence until redshift z~3 (if the star formed in-situ) or that the Milky Way has undergone merger events for at least ~12 Gyr (if the star was accreted by a dwarf satellite merger such as Gaia Enceladus).