arXiv 1604.030312016-04-11astro-ph.SR

钡星的化学丰度和运动学

Chemical abundances and kinematics of barium stars

D. B. de Castro, C. B. Pereira, F. Roig, E. Jilinski, N. A. Drake, C. Chavero, J. V. Sales Silva

备注：: 30 pages, 26 figures, 18 tables, accepted for publication in MNRAS
DOI：: 10.1093/mnras/stw815

摘要：

在本文中，我们提出了一个均匀的分析光球丰度的高分辨率光谱的基础上的样本182钡星和候选人。我们确定了大气参数，光谱距离，恒星质量，年龄，光度和刻度高度，径向速度，丰度的Na，Al，$alpha$ -元素，铁峰元素，和s-过程元素Y，Zr，La，Ce和Nd。我们采用了Kurucz的局部热力学平衡模式大气和光谱分析程序{ \sc moog}。我们发现钡星的金属丰度、温度和表面重力不能用单一的高斯分布来表示。$alpha$ -元素和铁峰元素的丰度与具有相同金属丰度的场巨星相似。钠在更演化的恒星中呈现出一定程度的富集，这可能归因于NeNa循环。正如预期的那样，钡星显示出由s过程产生的元素过剩。通过测量重元素的平均丰度模式（由[s/Fe]的比值给出），我们发现钡星呈现出不同程度的富集。我们还通过测量Ba峰和Zr峰元素的光球丰度得到了[hs/ls]比值。结果表明，[s/Fe]和[hs/ls]比值与金属丰度呈强反相关。我们的运动学分析表明，90%的钡星属于薄盘族。根据它们的光度，没有一颗钡星的亮度足以成为AGB星，也没有一颗钡星能够自我富集s过程元素。最后，我们确定钡星也遵循年龄-金属丰度关系。

英文摘要：

In this paper we present an homogeneous analysis of photospheric abundances based on high-resolution spectroscopy of a sample of 182 barium stars and candidates. We determined atmospheric parameters, spectroscopic distances, stellar masses, ages, luminosities and scale height, radial velocities, abundances of the Na, Al, $alpha$-elements, iron-peak elements, and s-process elements Y, Zr, La, Ce, and Nd. We employed the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code {\sc moog}. We found that the metallicities, the temperatures and the surface gravities for barium stars can not be represented by a single gaussian distribution. The abundances of $alpha$-elements and iron peak elements are similar to those of field giants with the same metallicity. Sodium presents some degree of enrichment in more evolved stars that could be attributed to the NeNa cycle. As expected, the barium stars show overabundance of the elements created by the s-process. By measuring the mean heavy-element abundance pattern as given by the ratio [s/Fe], we found that the barium stars present several degrees of enrichment. We also obtained the [hs/ls] ratio by measuring the photospheric abundances of the Ba-peak and the Zr-peak elements. Our results indicated that the [s/Fe] and the [hs/ls] ratios are strongly anti-correlated with the metallicity. Our kinematical analysis showed that 90% of the barium stars belong to the thin disk population. Based on their luminosities, none of the barium stars are luminous enough to be an AGB star, nor to become self-enriched in the s-process elements. Finally, we determined that the barium stars also follow an age-metallicity relation.

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英文摘要：

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