Precise Ages of Field Stars from White Dwarf Companions
Precise Ages of Field Stars from White Dwarf Companions
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DOI：
10.3847/1538-4357/aaee74
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发表时间：
2018-02
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影响因子：
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通讯作者：
M. Fouesneau;H. Rix;T. von Hippel;D. Hogg;H. Tian
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作者：
M. Fouesneau;H. Rix;T. von Hippel;D. Hogg;H. Tian
恒星和银河化学演化的观测测试需要了解恒星的物理参数、详细的元素丰度和精确的年龄。对于冷主序（MS）恒星，许多元素的丰度可以通过光谱测量，但年龄很难确定。如果 MS 星有白矮星 (WD) 伴星并且距离已知，情况就会有所不同，因为这样的双星系统的年龄可以根据冷却 WD 的光度特性精确确定。作为一项获得外场 MS 恒星精确年龄测定的初步研究，我们为这种宽双星系统确定了近 100 个候选星：一颗微弱的 WD，其 GPS1 自行与盖亚/TGAS 中一颗较亮的 MS 恒星相匹配，具有良好的视差 (σϖ/ϖ ≤ 0.05)。我们使用这个精确距离（假设对双星系统来说是常见的）通过 BASE-9 代码对 WD 的多波段光度测量进行建模，并推断每个双星系统的年龄。对于 42 (67) 个 MS-WD 系统，所得的年龄估计精确度为 ≤10% (≤20%)。我们的分析使迄今为止已知的具有精确距离的 MS-WD 系统的数量增加了一倍多，并且将具有精确年龄确定的此类系统的数量增加了一个数量级。随着 Gaia DR2 数据的出现，这种方法将适用于更大的样本，提供许多 MS 恒星的年龄（可以产生 20 多种元素的详细丰度），特别是在 2-8 岁的年龄范围内，其中已知的星团很少。
Observational tests of stellar and Galactic chemical evolution call for the joint knowledge of a star’s physical parameters, detailed element abundances, and precise age. For cool main-sequence (MS) stars the abundances of many elements can be measured from spectroscopy, but ages are very hard to determine. The situation is different if the MS star has a white dwarf (WD) companion and a known distance, as the age of such a binary system can then be determined precisely from the photometric properties of the cooling WD. As a pilot study for obtaining precise age determinations of field MS stars, we identify nearly 100 candidates for such wide binary systems: a faint WD whose GPS1 proper motion matches that of a brighter MS star in Gaia/TGAS with a good parallax (σϖ/ϖ ≤ 0.05). We model the WD’s multi-band photometry with the BASE-9 code using this precise distance (assumed to be common for the pair) and infer ages for each binary system. The resulting age estimates are precise to ≤10% (≤20%) for 42 (67) MS–WD systems. Our analysis more than doubles the number of MS–WD systems with precise distances known to date, and it boosts the number of such systems with precise age determination by an order of magnitude. With the advent of the Gaia DR2 data, this approach will be applicable to a far larger sample, providing ages for many MS stars (that can yield detailed abundances for over 20 elements), especially in the age range of 2–8 , where there are only few known star clusters.