太阳双星16天鹅座A和B的详细丰度：约束行星形成模型
Detailed Abundances of the Solar Twins 16 Cygni A and B: Constraining Planet Formation Models
摘要：
本文介绍了基于高分辨率、高信噪比阶梯光栅光谱技术对太阳双星16 Cyg A和16 Cyg B进行详细丰度分析的结果。天鹅座16 B已知拥有一颗巨行星，而天鹅座16 A周围尚未发现行星。恒星参数直接来自我们的高质量光谱，发现恒星在物理上相似，Delta_T_eff = +43 K，Delta_logg = -0.02 dex，Delta_xi = +0.10 km/s（在A-B意义上），与以前的发现一致。丰度的15个元素的推导和发现是无法区分的两颗恒星之间。每种元素的丰度相差<= 0.026 dex，平均差异为+0.003 +/- 0.015（sigma）dex。除了Li之外，之前已经证明16 Cyg B相对于16 Cyg A的损耗至少为4.5倍，这两颗恒星似乎在化学上是相同的。每颗恒星的丰度与元素的凝聚温度（T_c）呈正相关，趋势的斜率也难以区分。根据最近提出的建议，[m/H]-T_c关系的正斜率可能意味着类地行星在16 Cyg A或16 Cyg B附近都没有形成。根据行星形成模型讨论了16 Cyg系统的物理特征，并提出了16 Cyg A周围没有发现行星、16 Cyg A和B的Li丰度不同以及16 Cyg B b的偏心率的可能机制。
英文摘要：
Results of a detailed abundance analysis of the solar twins 16 Cyg A and 16 Cyg B based on high-resolution, high signal-to-noise ratio echelle spectroscopy are presented. 16 Cyg B is known to host a giant planet while no planets have yet been detected around 16 Cyg A. Stellar parameters are derived directly from our high-quality spectra, and the stars are found to be physically similar, with Delta_T_eff = +43 K, Delta_logg = -0.02 dex, and Delta_xi = +0.10 km/s (in the sense of A - B), consistent with previous findings. Abundances of 15 elements are derived and are found to be indistinguishable between the two stars. The abundances of each element differ by <= 0.026 dex, and the mean difference is +0.003 +/- 0.015 (sigma) dex. Aside from Li, which has been previously shown to be depleted by a factor of at least 4.5 in 16 Cyg B relative to 16 Cyg A, the two stars appear to be chemically identical. The abundances of each star demonstrate a positive correlation with the condensation temperature of the elements (T_c); the slopes of the trends are also indistinguishable. In accordance with recent suggestions, the positive slopes of the [m/H]-T_c relations may imply that terrestrial planets have not formed around either 16 Cyg A or 16 Cyg B. The physical characteristics of the 16 Cyg system are discussed in terms of planet formation models, and plausible mechanisms that can account for the lack of detected planets around 16 Cyg A, the disparate Li abundances of 16 Cyg A and B, and the eccentricity of the planet 16 Cyg B b are suggested.
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