论文标题
年轻银河矮人和巨型星星的锂，群众和运动学具有极高的[$α$/fe]比率
Lithium, masses, and kinematics of young Galactic dwarf and giant stars with extreme [$α$/Fe] ratios
论文作者
论文摘要
最近对大型银河恒星样品星星的光谱探索明星揭示了存在[$α$/fe]比率的红色巨人，鉴于其年龄相对年轻的年龄，它们异常高。我们重新审视Galah DR3调查，以寻找具有极高[$α$/fe]比率的矮人和巨人，也就是说，在-1.1和+0.4 dex之间，[$α$/fe/h]飞机在[$α$/fe/h]飞机上的上层1％。我们将这些异常值称为“ Ex $α$ FE”星。我们使用Galah DR3数据及其增值目录来追踪Ex $α$ Fe星的属性（丰度，群众，年龄和运动学）。我们研究了世俗进化的影响以及galah的幅度限制，以了解样品恒星的质量和金属性分布。我们还讨论了其他调查中对恒星高[$α$/fe]的相应偏见。我们发现矮人和巨人EX $α$ fe星比3 Gyr年轻，我们称为“ y-ex $α$ fe”之星。矮y-ex $α$ fe明星的锂丰度与年轻人和[fe/h]的Young [$α$/fe] - 正常矮人相似。特别是，两个种群中最年轻，最庞大的恒星表现出最高的LI丰度，A（li）〜3.5 Dex（即高于原始极值高2倍），而凉爽/较老的恒星表现出相同的LI耗尽模式，随着质量降低和年龄的增长而增加。此外，矮人和巨型y-ex $α$ fe星的[Fe/H]和质量分布与薄磁盘中的[$α$/fe] - 正常对应物的[$α$/fe] - 正常对应物没有差异，它们具有相同的运动特性。我们得出的结论是，Y-EX $α$ fe矮人和巨人的确很年轻，它们的质量分布没有特殊性，它们与Young [$α$/fe] - 正常恒星的不同[$α$/fe]的内容。但是，它们的起源尚不清楚。
Recent spectroscopic explorations of large Galactic stellar samples stars have revealed the existence of red giants with [$α$/Fe] ratios that are anomalously high, given their relatively young ages. We revisit the GALAH DR3 survey to look for both dwarfs and giants with extreme [$α$/Fe] ratios, that is, the upper 1% in the [$α$/Fe]-[Fe/H] plane over the range in [Fe/H] between -1.1 and +0.4 dex. We refer to these outliers as "ex$α$fe" stars. We used the GALAH DR3 data and their value-added catalog to trace the properties (abundances, masses, ages, and kinematics) of the ex$α$fe stars. We investigated the effects of secular evolution and the magnitude limitations of GALAH to understand the mass and metallicity distributions of the sample stars. We also discuss the corresponding biases in previous studies of stars with high [$α$/Fe] in other surveys. We find both dwarf and giant ex$α$fe stars younger than 3 Gyr, which we refer to as "y-ex$α$fe" stars. Dwarf y-ex$α$fe stars exhibit lithium abundances similar to those of young [$α$/Fe]-normal dwarfs at the same age and [Fe/H]. In particular, the youngest and most massive stars of both populations exhibit the highest Li abundances, A(Li)~3.5 dex (i.e., a factor of 2 above the protosolar value), while cooler/older stars exhibit the same Li depletion patterns increasing with both decreasing mass and increasing age. In addition, the [Fe/H] and mass distributions of both the dwarf and giant y-ex$α$fe stars do not differ from those of their [$α$/Fe]-normal counterparts found in the thin disk and they share the same kinematic properties. We conclude that y-ex$α$fe dwarfs and giants are indeed young, their mass distribution shows no peculiarity, and they differ from young [$α$/Fe]-normal stars by their extreme [$α$/Fe] content only. However, their origin remains unclear.
