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arXiv 2006.00901astro-ph.SR
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36颗开普勒次巨星-- II的星震学:根据详细模拟确定年龄

Asteroseismology of 36 Kepler subgiants -- II: Determining ages from detailed modelling

Tanda Li, Timothy R. Bedding, Jørgen Christensen-Dalsgaard, Dennis Stello, Yaguang Li, Matthew A. Keen

摘要:

详细的恒星振荡模型能够给出恒星年龄的精确估计,但推断的结果通常取决于用于年龄推断的模型参数。有36颗开普勒次巨星的高质量星震数据,其中包括对混合模式的精确测量。为了获得一个处理这些恒星的年龄的鲁棒性,我们首先研究了地震年龄的依赖关系的三个模型输入参数。我们发现,推断的年龄不随氦分数(Y)或混合长度参数而系统地变化,但强烈依赖于模型的金属丰度([M/H])。结果表明,亚巨星的年龄估计对模型的依赖性较小,因此比主序星或红巨星的年龄估计更可靠。然后,我们利用观测到的金属丰度,对相同的36颗开普勒次巨星的个别振荡频率进行建模,并以约15%的平均精度获得它们的年龄。与以前的年龄估计与不同的恒星代码或输入物理的比较显示出良好的协议(主要是在2#)。因此,我们认为,地震学确定的次巨星的年龄是不是很大的模型依赖。

英文摘要:

Detailed modelling of stellar oscillations is able to give precise estimates for stellar ages, but the inferred results typically depend on the adopted model parameters used for the age inference. High-quality asteroseismic data with precise measurements of mixed modes are available for 36 Kepler subgiants. To obtain a handle on the robustness of the ages for these stars, we first study the dependencies of seismic ages on three model input parameters. We find that inferred ages do not change systematically with the helium fraction (Y) or the mixing-length parameter but depend strongly on the metallicity ([M/H]) of the model. The results indicate that age estimates of subgiants have less model dependence and hence are more reliable than those of main-sequence stars or red giants. We then model individual oscillation frequencies of the same 36 Kepler subgiants, using observed metallicities, and obtain their ages with an average precision of ~15%. The comparison with previous age estimates with different stellar codes or input physics shows good agreement (mostly within 2#). We hence suggest that seismology-determined ages of subgiants are not greatly model-dependent.

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