A newly discovered active contact binary in the field of NGC 1348  

作　　者：Xiang-Song Fang Sheng-Hong Gu Ho-Keung Hui Chi-Tai Kwok Bill Yeung Kam-Cheung Leung 

机构地区：[1]National Astronomical Observatories / Yunnan Observatory, Chinese Academy of Sciences,Kunming 650011, China [2]Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China [3]Graduate University of Chinese Academy of Sciences, Beijing 100049, China [4]Hokoon Nature Education cum Astronomical Centre, Sik Sik-Yuen, Hong Kong, China [5]Hong Kong Astronomical Society, Hong Kong, China

出　　处：《Research in Astronomy and Astrophysics》2012年第1期93-103,共11页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos. 10373023 and 10773027);grants from the Sik Sik Yuen of Hong Kong,China

摘　　要：We present a CCD photometry study of a newly discovered active eclipsing binary in the field of open cluster NGC 1348 based on the first time-series photometric observation. From the minimum times, we determined an orbital period of P = 0.691363 d. Among our datasets, the BV（.RI）c light curves obtained in November 2008 were analyzed using the Wilson-Devinney light curve modeling tech- nique. Because of the uncertainty of the membership of this binary in open cluster NGC 1348, we have analyzed the photometric data in two cases with different primary effective temperatures： Case A （T1 = 7750K） and Case B （T1 = 5250K）. Our anal- yses reveal that, for Case A, it is a deep （f 〉 70%）, very low mass ratio （q - 0.096） binary system, indicating that it is now in the late evolution stage of a contact binary; while for Case B, it is a red system with extraordinarily long orbital period with respect to the period-color relation for normal contact binaries, which suggests that this binary has evolved off the main sequence. The well known O＇Connell effect （e.g., AB 0.03 mag） was found in the dataset obtained in November 2008, which could be due to the existence of starspots on the components, therefore the corresponding spot properties （for Case A： hot spot; for Case B： dark spot） were determined using the Wilson-Devinney code. With the purpose of analyzing the dark spot activity for Case B, we compared the light curves derived in different observing runs, and found that a slight change appeared from November to December, 2008, which indicates the evolution of spot activity on at least one component over a time scale of about one month.We present a CCD photometry study of a newly discovered active eclipsing binary in the field of open cluster NGC 1348 based on the first time-series photometric observation. From the minimum times, we determined an orbital period of P = 0.691363 d. Among our datasets, the BV（.RI）c light curves obtained in November 2008 were analyzed using the Wilson-Devinney light curve modeling tech- nique. Because of the uncertainty of the membership of this binary in open cluster NGC 1348, we have analyzed the photometric data in two cases with different primary effective temperatures： Case A （T1 = 7750K） and Case B （T1 = 5250K）. Our anal- yses reveal that, for Case A, it is a deep （f 〉 70%）, very low mass ratio （q - 0.096） binary system, indicating that it is now in the late evolution stage of a contact binary; while for Case B, it is a red system with extraordinarily long orbital period with respect to the period-color relation for normal contact binaries, which suggests that this binary has evolved off the main sequence. The well known O＇Connell effect （e.g., AB 0.03 mag） was found in the dataset obtained in November 2008, which could be due to the existence of starspots on the components, therefore the corresponding spot properties （for Case A： hot spot; for Case B： dark spot） were determined using the Wilson-Devinney code. With the purpose of analyzing the dark spot activity for Case B, we compared the light curves derived in different observing runs, and found that a slight change appeared from November to December, 2008, which indicates the evolution of spot activity on at least one component over a time scale of about one month.

关 键 词：stars： binaries： close -- stars： binaries： eclipsing -- stars： spots 

分 类 号：P145.2[天文地球—天体物理] TP314[天文地球—天文学]