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arXiv 1903.04765astro-ph.SR
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短周期截止点的接触双星I。十个日全食系统的统计和首次测光研究

Contact binaries at the short period cut-off I. statistics and the first photometric investigations of ten totally eclipsing systems

Kai Li, Qi-Qi Xia, Raul Michel, Shao-Ming Hu, Di-Fu Guo, Xing Gao, Xu Chen, Dong-Yang Gao

摘要:

接触双星的周期分布在0.22天处有一个非常尖锐的短周期截止。为了提供有价值的信息,这个短周期的限制,我们观察到10个全蚀接触双星的轨道周期接近这个截止。通过W-D程序的详细分析,我们确定其中两个系统为A亚型接触双星,另两个系统为W亚型接触双星,并且所有目标都表现为浅接触构型。一半的目标显示出恒星黑子活动,其中四个有第三光。对已有研究的USPCBs进行了统计分析,得到了55种USPCBs的物理参数。得到了这些系统的一些共同性质。通过对USPCBs的周期-颜色图的研究,我们发现USPCBs的周期-颜色关系不同于其它的W UMa型接触双星,USPCBs是贫金属的老星。此外,通过色密度图的绘制,讨论了系统的演化状态。我们推导出的USPCBs的两个组件的演化状态显示出相同的特征,其他接触双星,尽管较小的质量造成的较慢的演化状态。我们认为Rucinski(1992)提出的完全对流极限和Stepien(2006)提出的AML理论都能产生短周期截止,并且在一定条件下,通过去除主食双星的角动量,第三伴星在短周期接触双星的形成过程中是非常重要的。

英文摘要:

The period distribution of contact binaries exhibits a very sharp short period cut-off at 0.22 days. In order to provide valuable information on this short period limit, we observed ten totally eclipsing contact binaries with orbital periods near this cut-off. By detailed analysis using W-D code, we determined that two of these systems are A-subtype contact binaries while the others are W-subtype contact binaries and all the targets show shallow contact configurations. Half of the targets exhibit stellar spot activity and four of them have third light. A statistical work on well studied USPCBs was carried out, and physical parameters of fifty-five USPCBs were obtained. Some common properties for these systems were derived. Due to the study of the period-color diagram of USPCBs, we found that the period-color relation of USPCBs is different from other W UMa type contact binaries and USPCBs are metal poor old stars. In addition, the evolutionary states of these systems were discussed by constructing the color-density diagram. We derived that the evolutionary states of the two components of USPCBs show identical characteristics of other contact binaries despite slower evolutionary status caused by smaller mass. We suggested that both the fully convective limit claimed by Rucinski (1992) and the AML theory recommended by Stepien (2006) can produce the short period cut-off and a tertiary companion is very important during the formation of the short period contact binaries by removing angular momentum from the host eclipsing pairs under certain circumstances.

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