LL Com: A Near-contact Total Eclipsing Binary at a Key Stage of Evolution
LL Com: A Near-contact Total Eclipsing Binary at a Key Stage of Evolution
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LL Com：处于演化关键阶段的近接触全食双星
DOI：
10.3847/1538-3881/ab322c
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发表时间：
2019
影响因子：
5.3
通讯作者：
Er-Gang Zhao
中科院分区：
文献类型：
--
作者：
Ke Hu;Kun Chen;Fu-Yuan Xiang;Yun-Xia Yu;Er-Gang Zhao
尽管大约60年前发现了一个天琴座型食双星系统LL Com，但迄今为止，关于它的详细测光和轨道周期变化的研究还很少。在本文中，我们提出了第一个多波段的电荷耦合器件测光光变曲线，从一个显着的光度降低周围的主要日食被揭示。基于LAMOST数据，我们首先确定LL Com的光谱为F1 V，然后使用2015年版本的Wilson-Devinney代码分析光变曲线。事实上，LL Com是一个近接触的二进制系统与半分离的配置，其中第二个组件只填充其罗氏瓣和主要组件填充超过95%的罗氏瓣，建议通过光度的解决方案。此外，根据档案测光和以前公布的时间的最低值，一个长期的增加率被发现，这意味着一个连续的质量转移从中学到小学。利用光度的解决方案和单粒子轨迹的模拟，我们提出了一个冷点的存在的表面上的主要组成部分。这个冷点可以由质量流期间发生的撞击自然产生，它也成功地解释了光变曲线中的光度降低。最后，结合热弛豫振荡理论和Roche-Lobe模型，我们得出了LL Com正从半脱离态向脱离态转变的结论。
Despite the discovery of LL Com, a Lyrae-type eclipsing binary system, approximately 60 yr ago, little has been found concerning its detailed photometry and orbital-period change until now. In this paper, we present the first multi-band charge-coupled-device photometric light curves, from which a significant luminosity reduction around the primary eclipse is revealed. Based on LAMOST data, we first determined LL Com’s spectrum as F1V and then analyzed the light curves with the 2015 version of the Wilson-Devinney code. The fact that LL Com is a near-contact binary system with a semi-detached configuration, where the secondary component only fills its Roche lobe and the primary component fills more than 95% of its Roche lobe, is suggested through the photometric solution. In addition, according to archival photometry and previously published times of minima, a secular period increase at a rate of was found, which implies a continuous mass transfer from the secondary to the primary. Utilizing the photometric solution and the simulations of single-particle trajectories, we propose the existence of a cool spot on the surface of the primary component. This cool spot can be naturally produced by the impacts that occur during mass flow, and it also successfully interprets the luminosity reduction in the light curves. Finally, with the combination of thermal relaxation oscillation theory and the Roche-Lobe model, we conclude that LL Com is transitioning from the semi-detached to the detached phase.