A Bayesian Analysis of Physical Parameters for 783 Kepler Close Binaries: Extreme-mass-ratio Systems and a New Mass Ratio versus Period Lower Limit
A Bayesian Analysis of Physical Parameters for 783 Kepler Close Binaries: Extreme-mass-ratio Systems and a New Mass Ratio versus Period Lower Limit
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DOI：
10.3847/1538-4365/ac75bd
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发表时间：
2022-02
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影响因子：
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通讯作者：
H. Kobulnicky;L. Molnar;Evan M. Cook;L. E. Henderson
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文献类型：
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作者：
H. Kobulnicky;L. Molnar;Evan M. Cook;L. E. Henderson
接触双星星星系统代表了双星演化的长寿命倒数第二阶段。它们的物理参数的人口统计信息的二元进化途径和最终产品的理解。我们利用光变曲线和新的光谱学对开普勒场中密近双星长周期（P > 0.5天）尾的十个（近）接触系统进行了初步研究。我们使用PHOEBE光变曲线模型计算贝叶斯概率的五个主要系统参数。从光谱中测得的质量比和第三光贡献与从光变曲线中推断的结果吻合得很好。试点研究系统有极端的质量比q 0.5天，是系统与q > 0.8。存在一个经验质量比下限qmin（P）<$0.05 -0.15，低于该下限则不存在接触系统，这支持了通过在质量和角动量守恒的约束下对接触系统的演化进行建模而获得的一组新的理论预测。合并前系统应处于长周期，并接近这个质量比下限，从P = 0.74天的q = 0.044上升到P = 2.0天的q = 0.15。这些发现支持一种情况，即核演化的主要（更大质量）星星驱动质量转移到主要的，从而移动系统向极端q和更大的P，直到发病的达尔文不稳定性在qmin沉淀合并。
Contact binary star systems represent the long-lived penultimate phase of binary evolution. Population statistics of their physical parameters inform an understanding of binary evolutionary pathways and end products. We use light curves and new optical spectroscopy to conduct a pilot study of ten (near) contact systems in the long-period (P > 0.5 days) tail of close binaries in the Kepler field. We use PHOEBE light-curve models to compute Bayesian probabilities on five principal system parameters. Mass ratios and third-light contributions measured from spectra agree well with those inferred from the light curves. Pilot study systems have extreme mass ratios q 0.5 days, as are systems with q > 0.8. There exists an empirical mass ratio lower limit qmin(P) ≈ 0.05–0.15 below which contact systems are absent, supporting a new set of theoretical predictions obtained by modeling the evolution of contact systems under the constraints of mass and angular momentum conservation. Premerger systems should lie at long periods and near this mass ratio lower limit, which rises from q = 0.044 for P = 0.74 days to q = 0.15 at P = 2.0 days. These findings support a scenario whereby nuclear evolution of the primary (more massive) star drives mass transfer to the primary, thus moving systems toward extreme q and larger P until the onset of the Darwin instability at qmin precipitates a merger.