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标题：TY Pup: A Low-mass-ratio and Deep Contact Binary as a Progenitor Candidate of Luminous Red Novae
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作者：T. Sarotsakulchai ; S.-B. Qian ; B. Soonthornthum 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：156
期号：5
页码：1-11
DOI：10.3847/1538-3881/aadcfa
语种：English
出版社：American Institute of Physics
摘要：TY Pup is a well-known bright eclipsing binary with an orbital period of 0.8192 days. New light curves in B, V, (RI) C bands were obtained with the 0.61 m reflector robotic telescope (PROMPT-8) at CTIO in Chile during 2015 and 2017. By analyzing those photometric data with the W–D method, it is found that TY Pup is a low-mass-ratio (q∼0.184) and deep-contact binary with a high fill-out factor (84.3%). An investigation of all available times of minimum light including three new ones obtained with the 60 cm and the 1.0m telescopes at Yunnan Observatories in China indicates that the period change of TY Pup is complex. An upward parabolic variation in the O−C diagram is detected to be superimposed on a cyclic oscillation. The upward parabolic change reveals a long-term continuous increase in the orbital period at a rate of dP/dt=5.57(±0.08)×10 −8 daysyr −1 . The period increase can be explained by mass transfer from the less massive component (M 2 ∼0.3 M e ) to the more massive one (M 1 ∼1.65 M e ). The binary will be merging when it meets the criterion that the orbital angular momentum is less than three times the total spin angular momentum, i.e., J orb <3J rot . This suggests that the system will finally merge into a rapid-rotating single star and may produce a luminous red nova. The cyclic oscillation in the O−C diagram can be interpreted by the light-travel time effect via the presence of a third body.
关键词：binaries: close;binaries: eclipsing;stars: evolution;stars: individual (TY Pup)