Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67-猫眼课题宝

DOI：

10.3847/1538-4357/aab612

发表时间：

2018-03

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

D. Souto;K. Cunha;V. Smith;C. Prieto;C. Prieto;D. A. García-Hernández;D. A. García-Hernández;M. Pinsonneault;Parker H. Holzer;P. Frinchaboy;J. Holtzman;J. A. Johnson;H. Jönsson;S. Majewski;M. Shetrone;J. Sobeck;G. Stringfellow;J. Teske;O. Zamora;O. Zamora;G. Zasowski;R. Carrera;K. Stassun;J. G. Fernández-Trincado;J. G. Fernández-Trincado;S. Villanova;D. Minniti;F. Santana

对年龄约4 Gyr的太阳金属丰度老疏散星团M67的8个高概率恒星成员，导出了14种元素的详细化学丰度分布。这八颗恒星由四对组成，每对都占据着恒星演化的不同阶段：两颗G矮星、两颗关闭星、两颗G亚巨星和两颗红团（RC） K巨星。丰度分析使用来自阿帕奇点天文台星系演化实验调查的近红外高分辨率光谱（λ1.5-1.7 μm），并得出C， N， O, Na, Mg, Al, Si， K, Ca, Ti， V, Cr， Mn和Fe的丰度。我们得到的恒星参数和2M08510076+1153115的金属丰度表明，这颗恒星是一对太阳双胞胎，所有元素的丰度与太阳的差异≤0.04指数。在每一类恒星中发现了化学同质性（~ 0.02指数），而在不同进化阶段发现了显著的丰度变化（~ 0.05-0.20指数）；关闭星通常具有最低的丰度，而RCs往往具有最大的丰度。对lte衍生丰度的非lte修正不太可能解释这些差异。将得到的铁、镁、硅和钙的丰度与最近公布的包括化学扩散在内的恒星模型的表面丰度进行了详细的比较，结果表明，作为恒星质量的函数，观测到的丰度与预测的丰度之间存在很好的匹配。这种一致性将表明在M67的恒星成员中检测到化学扩散过程。

Detailed chemical abundance distributions for 14 elements are derived for eight high-probability stellar members of the solar metallicity old open cluster M67 with an age of ∼4 Gyr. The eight stars consist of four pairs, with each pair occupying a distinct phase of stellar evolution: two G dwarfs, two turnoff stars, two G subgiants, and two red clump (RC) K giants. The abundance analysis uses near-IR high-resolution spectra (λ1.5–1.7 μm) from the Apache Point Observatory Galactic Evolution Experiment survey and derives abundances for C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe. Our derived stellar parameters and metallicity for 2M08510076+1153115 suggest that this star is a solar twin, exhibiting abundance differences relative to the Sun of ≤0.04 dex for all elements. Chemical homogeneity is found within each class of stars (∼0.02 dex), while significant abundance variations (∼0.05–0.20 dex) are found across the different evolutionary phases; the turnoff stars typically have the lowest abundances, while the RCs tend to have the largest. Non-LTE corrections to the LTE-derived abundances are unlikely to explain the differences. A detailed comparison of the derived Fe, Mg, Si, and Ca abundances with recently published surface abundances from stellar models that include chemical diffusion provides a good match between the observed and predicted abundances as a function of stellar mass. Such agreement would indicate the detection of chemical diffusion processes in the stellar members of M67.

Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67

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