arXiv 1909.063752019-09astro-ph.SRastro-ph.GA

从银河系运动学测量的短周期双星的寿命

Lifetime of short-period binaries measured from their Galactic kinematics

Hsiang-Chih Hwang, Nadia Zakamska

备注：: Accepted for publication in MNRAS. Figure 5 is the key result
DOI：: 10.1093/mnras/staa400

摘要：

由于相当一部分恒星是在多个系统中，双星在恒星演化中扮演着至关重要的角色。在短周期（<1天）的二元特征中，年龄仍然是最难测量的。在本文中，我们通过短周期双星的运动学约束其寿命。利用盖亚数据发布2的运动学信息和{ \it广域红外勘测探测器}（WISE）的光变曲线，我们研究了作为体积有限的主序样本运动学函数的食二进制分数。我们发现食双星分数在切向速度为$10^{1.3-1.6}$ km/s处达到峰值，并向低速和高速端减小。这意味着厚盘星和晕星的食双星比薄盘星小$\gtrsim 10$倍。这是进一步支持的食双星分数对银河系纬度的依赖性。使用银河系模型，我们表明我们的结果与任何已知的二元分数对金属丰度的依赖性不一致。相反，我们的最佳拟合模型表明，这些短周期双星的形成延迟了0.6-3 Gyr，消失的时间小于厚盘的年龄。$\gtrsim0.6$ Gyr的延迟形成时间意味着这些短周期主序星双星不能由前主序星相互作用和Kozai-Lidov机制单独形成，并表明磁制动在它们的形成中起着关键作用。因为我们的样本的主序列寿命长于14 Gyr，如果短周期双星在老人口中的消失是由于其有限的寿命，我们的研究结果意味着大多数（$\gtrsim90$ %）短周期双星在我们的样本合并在其主序列阶段。

英文摘要：

As a significant fraction of stars are in multiple systems, binaries play a crucial role in stellar evolution. Among short-period (<1 day) binary characteristics, age remains one of the most difficult to measure. In this paper, we constrain the lifetime of short-period binaries through their kinematics. With the kinematic information from Gaia Data Release 2 and light curves from {\it Wide-field Infrared Survey Explorer} (WISE), we investigate the eclipsing binary fraction as a function of kinematics for a volume-limited main-sequence sample. We find that the eclipsing binary fraction peaks at a tangential velocity of $10^{1.3-1.6}$ km/s, and decreases towards both low and high velocity end. This implies that thick disk and halo stars have eclipsing binary fraction $\gtrsim 10$ times smaller than the thin-disk stars. This is further supported by the dependence of eclipsing binary fraction on the Galactic latitude. Using Galactic models, we show that our results are inconsistent with any known dependence of binary fraction on metallicity. Instead, our best-fit models suggest that the formation of these short-period binaries is delayed by 0.6-3 Gyr, and the disappearing time is less than the age of the thick disk. The delayed formation time of $\gtrsim0.6$ Gyr implies that these short-period main-sequence binaries cannot be formed by pre-main sequence interaction and the Kozai-Lidov mechanism alone, and suggests that magnetic braking plays a key role in their formation. Because the main-sequence lifetime of our sample is longer than 14 Gyr, if the disappearance of short-period binaries in the old population is due to their finite lifetime, our results imply that most ($\gtrsim90$%) short-period binaries in our sample merge during their main-sequence stage.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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英文摘要：

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