NLTE Analysis of Copper Lines in Different Stellar Populations
NLTE Analysis of Copper Lines in Different Stellar Populations
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不同恒星族中铜线的 NLTE 分析
DOI：
10.3847/1538-4357/aacb22
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Zhao G.
中科院分区：
文献类型：
--
作者：
Shi J.R.;Yan H.Y.;Zhou Z. M.;Zhao G.
利用ESO VLT望远镜的UVES光谱仪获得的高分辨率、高信噪比的光谱，测定了29颗贫金属星的铜丰度。我们的样本由银河系晕、厚盘和薄盘的恒星组成，[Fe/H]的范围从100 - 3.2到100 - 0.0 dex。研究了铜I线的非局域热力学平衡（NLTE）效应，并对包含97项和1089条线跃迁的铜原子模型进行了线形成计算。我们采用最近计算的Cu I的光电离截面，通过比较我们的样品星的理论和观测的线轮廓，研究了氢碰撞。基于光谱合成方法，推导了局部热力学平衡（LTE）和NLTE的铜丰度。我们的研究结果表明，铜I线的NLTE效应是重要的贫金属星，特别是非常贫金属星，这些影响取决于金属丰度。对于非常贫金属的恒星，NLTE的丰度修正与标准LTE的计算相比达到了0.5 dex。我们的结果表明，当考虑NLTE效应时，贫金属星的[Cu/Fe]丰度不足（约为0.5 dex）。
The copper abundances of 29 metal-poor stars are determined based on the high-resolution, high-signal-to-noise ratio spectra from the UVES spectrograph at the ESO VLT telescope. Our sample consists of the stars of the Galactic halo, thick- and thin-disk, with [Fe/H] ranging from ˜-3.2 to ˜0.0 dex. The non-local thermodynamic equilibrium (NLTE) effects of Cu I lines are investigated, and line formation calculations are presented for an atomic model of copper including 97 terms and 1089 line transitions. We adopted the recently calculated photoionization cross sections of Cu I, and investigated the hydrogen collision by comparing the theoretical and observed line profiles of our sample stars. The copper abundances are derived for both local thermodynamic equilibrium (LTE) and NLTE based on the spectrum synthesis methods. Our results show that the NLTE effects for Cu I lines are important for metal-poor stars, in particular for very metal-poor stars, and these effects depend on the metallicity. For very metal-poor stars, the NLTE abundance correction reaches as large as ˜+0.5 dex compared to standard LTE calculations. Our results indicate that [Cu/Fe] is under-abundant for metal-poor stars (˜-0.5 dex) when the NLTE effects are included.