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标题：A Study of the Kepler K2 Variable EPIC 211957146 Exhibiting a Variable O’ Connell Effect
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作者：K. Sriram ; S. Malu ; C. S. Choi 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2017
卷号：153
期号：5
DOI：10.3847/1538-3881/aa6893
语种：English
出版社：American Institute of Physics
摘要：We present the multi-band photometric and spectroscopic study of an over-contact binary system, EPIC 211957146. The light curves exhibit a variable O' Connell effect, confirmed from our observational data and the Kepler K2 data. The best photometric solution incorporating a dark spot over the primary component unveils that the system has a low-mass ratio (q ~ 0.17) and a high inclination (i ~ 85°). To confirm the solution and constrain the uncertainty, Monte-Carlo simulations are performed and the results are reported. Based on the O–C diagram analysis, we see that the variable shows a period increase at the rate of dP/dt ~ 1.06 × 10−6 days yr−1, which is higher than the theoretically predicted value. Presence of a third body having a period of ~16.23 years is evident from the O–C diagram. No filled-in effect is observed in the Hα line, while the effect is vividly present in the Na line. From the Kepler K2 data, we found that the primary and secondary minima exhibit an anti-correlated O–C variation followed by an erratic behavior. This is possibly caused by the longitudinal motion of the spot, and hence, we set a lower limit of ~40 days for the spot modulation. We also observe a possibly associated photometric difference in the primary depth by comparing our light curves with Kepler K2 normalized light curves. This system has a low-mass ratio and a high fill-out factor, and, theoretically, such a physical configuration would lead to a merger.
关键词：binaries: close;binaries: eclipsing;stars: activity;stars: evolution;stars: general;stars: individual (EPIC 211957146) Supporting material: data behind figure; machine-readable table