Elemental abundances in the atmosphere of clump giants
Elemental abundances in the atmosphere of clump giants
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DOI：
10.1051/0004-6361:20065141
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发表时间：
2006-05
影响因子：
6.5
通讯作者：
T. Mishenina;O. Bienaym'e;T. Gorbaneva;C. Charbonnel;C. Soubiran;S. Korotin;V. Kovtyukh
中科院分区：
文献类型：
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作者：
T. Mishenina;O. Bienaym'e;T. Gorbaneva;C. Charbonnel;C. Soubiran;S. Korotin;V. Kovtyukh
目标。本文的目的是提供一个高精度的大样本的本地集群巨星的基本参数和丰度。这项研究是一个大项目的一部分，该项目正在研究银河系盘中恒星的垂直分布以及银河系的化学和动力学演化。方法.样本组的集群星的选择是通过对附近的依巴谷星应用颜色绝对星等窗口进行的。用线深比法估算了有效温度。用两种方法（第一种是基于铁的电离平衡的方法，第二种是基于$\ion{Ca}{i}$6162.17 A线的翼拟合的方法）确定表面重力（$\log\，{g}$）。碳和氮的丰度从分子合成光谱获得，镁和钠的丰度使用非LTE近似推导。采用了没有原子扩散和旋转诱导混合的恒星演化的“经典”模型。结果本文测定了银河系盘177颗巨星系团的大气参数（T_{\rmeff}}$，$\log\，{g}$，[Fe/H]，${V_{t}}$）和Li，C，N，O，Na，Mg，Si，Ca，Ni的丰度。检测到碳的丰度不足、氮的丰度过剩和氧的“正常”丰度。发现了少量的钠过剩，并探讨了根据其化学成分和演化轨迹来选择簇状巨星的可能性。结论.基于经典恒星演化模型的理论预测与观测到的碳和氮在第一次疏浚事件后的表面变化符合得很好。巨星的O、Mg、Ca、Si（α -元素）和Ni（铁峰元素）丰度对[Fe/H]的依赖性与矮星相同。这使我们能够使用这样的丰度比来研究银河系的化学和动力学演化。
Aims. The aim of this paper is to provide the fundamental parameters and abundances for a large sample of local clump giants with a high accuracy. This study is a part of a big project, in which the vertical distribution of the stars in the Galactic disc and the chemical and dynamical evolution of the Galaxy are being investigated. Methods. The selection of clump stars for the sample group was made applying a colour-absolute magnitude window to nearby Hipparcos stars. The effective temperatures were estimated by the line depth ratio method. The surface gravities ($\log\,{g}$) were determined by two methods (the first one was the method based on the ionization balance of iron and the second one was the method based on fitting of the wings of the $\ion{Ca}{i}$ 6162.17 A line). The abundances of carbon and nitrogen were obtained from the molecular synthetic spectrum, and the Mg and Na abundances were derived using the non-LTE approximation. The “classical" models of stellar evolution without atomic diffusion and rotation-induced mixing were employed. Results. The atmospheric parameters (${T_{\rm eff}}$, $\log\,{g}$, [Fe/H], ${V_{t}}$) and Li, C, N, O, Na, Mg, Si, Ca, and Ni abundances in 177 clump giants of the Galactic disc were determined. The underabundance of carbon, overabundance of nitrogen, and “normal” abundance of oxygen were detected. A small sodium overabundance was found. A possibility of a selection of the clump giants based on their chemical composition and the evolutionary tracks was explored. Conclusions. The theoretical predictions based on the classical stellar evolution models are in good agreement with the observed surface variations of the carbon and nitrogen just after the first dredge-up episode. The giants show the same behaviour of the dependencies of O, Mg, Ca, and Si ( α -elements) and Ni (iron-peak element) abundances vs. [Fe/H] as dwarfs do. This allows us to use such abundance ratios to study the chemical and dynamical evolution of the Galaxy.