标题： 银河晕及其矮卫星的形成：NLTE-1D丰度分析。 IV. Segue 1、Triangulum II和Coma Berenices UFDs 显示英文标题

标题： The formation of the Milky Way halo and its dwarf satellites: a NLTE-1D abundance analysis. IV. Segue 1, Triangulum II, and Coma Berenices UFDs

摘要： 我们给出了Segue 1（七颗恒星）、Coma Berenices（三颗恒星）和Triangulum II（一颗恒星）这三个贫金属超 faint矮星系中从碳到钡的化学元素的大气参数和丰度。这些有效温度依赖于使用SAI MSU高加索天文台2.5米望远镜在可见光和红外波段获得的新光度观测数据。在非局部热力学平衡（NLTE）线形成下推导了多达十四种化学元素的丰度，并且在局部热力学平衡（LTE）下获得了多达五种更多元素的丰度。我们首次给出了Segue 1的S1和S4中的氧丰度，ComaBer的S2和Tri II的S40中的硅丰度，以及Segue 1的S1-S6和ComaBer的S1-S3中的钾丰度和Segue 1的S7中的钡丰度。Segue 1的三颗恒星，Coma Berenices的两颗恒星和Triangulum II的一颗恒星具有非常低的[Na/Mg]值，范围从-1.08到-1.67 dex，这在文献中通常归因于大质量无金属恒星核合成产生的奇偶效应。我们将这种化学性质解释为第一代恒星的足迹，由于对样本恒星的化学丰度模式贡献的核合成事件数量较少，因此没有被模糊。我们在Coma Berenices，Segue 1和Triangulum II中的NLTE锶和钡丰度报告了超 faint矮星系中[Sr/Ba]丰度比低于经典矮椭球星系和银河晕。然而，与大质量星系一样，在超 faint矮星系中[Sr/Ba]并不恒定，它可以高于纯r过程比率。我们提出了在银河早期演化阶段贫金属双星中锶产生的假设。 显示英文摘要

摘要： We present atmospheric parameters and abundances for chemical elements from carbon to barium in metal-poor stars in Segue 1 (seven stars), Coma Berenices (three stars), and Triangulum II (one star) ultra-faint dwarf galaxies (UFDs). The effective temperatures rely on new photometric observations in the visible and infra-red bands, obtained with the 2.5 m telescope of the SAI MSU Caucasian observatory. Abundances of up to fourteen chemical elements were derived under the non-local thermodynamic equilibrium (NLTE) line formation, and LTE abundances were obtained for up to five more elements. For the first time we present abundance of oxygen in Seg 1 S1 and S4, silicon in ComaBer S2 and Tri II S40, potassium in Seg 1 S1-S6 and ComaBer S1-S3, and barium in Seg 1 S7. Three stars in Segue 1, two stars in Coma Berenices, and Triangulum II star have very low [Na/Mg] of -1.08 to -1.67 dex, which is usually attributed in the literature to an odd-even effect produced by nucleosynthesis in massive metal-free stars. We interpret this chemical property as a footprint of first stars, which is not blurred due to a small number of nucleosynthesis events that contributed to chemical abundance patterns of the sample stars. Our NLTE abundances of Sr and Ba in Coma Berenices, Segue 1, and Triangulum II report on lower [Sr/Ba] abundance ratio in the UFDs compared to that in classical dwarf spheroidal galaxies and the Milky Way halo. However, in UFDs, just as in massive galaxies, [Sr/Ba] is not constant and it can be higher than the pure r-process ratio. We suggest a hypothesis of Sr production in metal-poor binaries at the earliest epoch of galactic evolution.