CSS J075415.6+191052 and NW Leo: Two Contact Binaries at Different Evolutionary Stages

作     者：Xu-Dong Zhang Sheng-Bang Qian Er-Gang Zhao Qi-Jun Zhi Ai-Jun Dong Bin Zhang Xu-Dong Zhang;Sheng-Bang Qian;Er-Gang Zhao;Qi-Jun Zhi;Ai-Jun Dong;Bin Zhang

作者机构：School of Physics and Electronic ScienceGuizhou Normal University550025 GuiyangChina Guizhou Provincial Key Laboratory of Radio Astronomy and Data ProcessingGuizhou Normal UniversityGuiyang 550025 GuiyangChina Yunnan ObservatoriesChinese Academy of Sciences(CAS)650216 KunmingChina University of Chinese Academy of Sciences(UCAS)100049 BeijingChina 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2022年第22卷第2期

页      面：118-127页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 11933008 and 11903076) the Science Foundation of Yunnan Province (202001AT070051) the Foundation of Science and Technology of Guizhou Province (Nos. (2016)4008, (2017)5726-37) the Foundation of Guizhou Provincial Education Department (No. KY(2020)003)。 

主　　题：(stars:)binaries:eclipsing stars:evolution stars:individual(CSS J075415.6+191052 NW Leo) 

摘      要：Multi-color light curves of CSS J075415.6+191052 and NW Leo are presented and the photometric solutions suggest that CSS J075415.6+191052 is an A-subtype contact binary with low mass ratio(q = 0.178) while NW Leo has a high mass ratio(q = 0.707). For CSS J075415.6+191052, the RI light curves show weakening around the left shoulder of the secondary minimum, which indicates that there may be a dark spot on the secondary component. However, the light curves of BV bands are totally symmetric. It is unreasonable if the dark spot is caused by magnetic activity or mass transfer between the two components. Therefore, weakening of the light curves in this contact binary is caused by something else. A possible explanation is mass transferring from the primary component to the common convective envelope through the inner Lagrangian point, and this part of the mass, for some reason, weakens the RI bands of light from the secondary component. O-C analysis of NW Leo reveals a cyclic period change with a modulation period of 4.7 yr, which may be caused by the light travel time effect of a third body. The positions of CSS J075415.6+191052 and NW Leo in the P–J′_(orb)diagram indicate that CSS J075415.6+191052 mainly abides by the angular momentum loss theory while NW Leo is dominated by the thermal relaxation oscillation theory.