arXiv 2212.025532022-12astro-ph.SR

相接双星的质量比分布

Mass-ratio distribution of contact binary stars

Milan Pešta, Ondřej Pejcha

备注：: Accepted to A&A. 28 pages, 22 figures, 4 tables
发表信息：: A&A 672, A176 (2023)
DOI：: 10.1051/0004-6361/202245613

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AI总结：

本文利用 Kepler 与 Gaia 数据结合贝叶斯推断，从光变曲线振幅分布推得相接双星临界质量比 q_min，揭示其与组分结构的相关性。

摘要：

相接双星的质量比 $q$ 由于质量转移、磁制动和热弛豫振荡而演化至较小值，直到跨越临界阈值 $q_\ ext{min}$。当这种情况发生时，双星会经历潮汐达尔文不稳定性，导致双星组分的快速并合以及系统可观测的增亮。迄今为止，$q$ 的分布尚未在足够大的相接双星群体上进行测量，因为确定单个相接双星的 $q$ 通常需要光谱观测。但正如先前所展示的，可以从观测到的光变曲线振幅分布来推断整个相接双星群体的质量比分布。我们采用贝叶斯推断，从 Kepler Eclipsing Binary Catalog 中获取相接双星候选体样本，并结合 Gaia 的数据和有效温度估计。我们为每个候选体赋予其属于晚型或早型相接双星的概率。总体而言，我们的样本包含约 300 个晚型和 200 个早型相接双星候选体。我们假设质量比由指数为 $b$ 且截断于 $q_\ ext{min}$ 的幂律描述，并对振幅分布进行建模。对于周期长于 0.3 天的晚型相接双星，我们发现 $q_\ ext{min}=0.087^{+0.024}_{-0.015}$。对于周期较短的晚型双星，我们发现 $q_\ ext{min}=0.246^{+0.029}_{-0.046}$，但样本较小。对于周期短于 1 天的早型相接双星，我们得到 $q_\ ext{min}=0.030^{+0.018}_{-0.022}$。这些结果表明 $q_\ ext{min}$ 依赖于双星组分的结构，并且与先前的理论预测大致相符。我们的方法可以很容易地扩展到来自 TESS 和其他空间巡天任务的大型相接双星样本。

英文摘要：

The mass ratio $q$ of a contact binary star evolves due to mass transfer, magnetic braking, and thermal relaxation oscillations to small values until it crosses a critical threshold $q_\text{min}$. When that happens, the binary undergoes the tidal Darwin instability, leading to a rapid coalescence of the components and observable brightening of the system. So far, the distribution of $q$ has not been measured on a sufficiently large population of contact binary stars, because the determination of $q$ for a single contact binary usually requires spectroscopy. But as was shown previously, it is possible to infer the mass-ratio distribution of the entire population of contact binaries from the observed distribution of their light curve amplitudes. Employing Bayesian inference, we obtain a sample of contact binary candidates from the Kepler Eclipsing Binary Catalog combined with data from Gaia and estimates of effective temperatures. We assign to each candidate a probability of being a contact binary of either late or early type. Overall, our sample includes about 300 late-type and 200 early-type contact binary candidates. We model the amplitude distribution assuming that mass ratios are described by a power law with an exponent $b$ and a cut off at $q_\text{min}$. We find $q_\text{min}=0.087^{+0.024}_{-0.015}$ for late-type contact binaries with periods longer than 0.3 days. For late-type binaries with shorter periods, we find $q_\text{min}=0.246^{+0.029}_{-0.046}$, but the sample is small. For early type contact binary stars with periods shorter than 1 day, we obtain $q_\text{min}=0.030^{+0.018}_{-0.022}$. These results indicate a dependence of $q_\text{min}$ on the structure of the components and are broadly compatible with previous theoretical predictions. Our method can be easily extended to large samples of contact binaries from TESS and other space-based surveys.

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