An orbital period investigation of the Algol-type eclipsing binary VW Hydrae

作     者：Jia Zhang Sheng-Bang Qian Boonrucksar Soonthomthum Jia Zhang1,2, Sheng-Bang Qian1 and Boonrucksar Soonthornthum3 1 National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China;2 Graduate School of the Chinese Academy of Sciences, Beijing 100039, China 3 National Astronomical Research Institute of Thailand/Ministry of Science and Technology, Bangkok, Thailand

作者机构：National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China National Astronomical Research Institute of Thailand/Ministry of Science and TechnologyBangkok Thailand 

出 版 物：《Chinese Journal of Astronomy and Astrophysics》 (中国天文和天体物理学报（英文版）)

年 卷 期：2009年第9卷第3期

页      面：307-314页

核心收录：

学科分类：070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 08[工学] 081202[工学-计算机软件与理论] 0812[工学-计算机科学与技术（可授工学、理学学位）] 

基　　金：Supported by the National Natural Science Foundation of China 

主　　题：stars binaries close - stars binaries eclipsing - multiple stars - stars individual (VW Hya) 

摘      要：Orbital period variations of the Algol-type eclipsing binary, VW Hydrae, are analyzed based on one newly determined eclipse time and the other times of light minima collected from the literature. It is discovered that the orbital period shows a continuous increase at a rate ofdP/dt = ＋6.34 × 10^-7 d yr^-1 while it undergoes a cyclic change with an amplitude of 0.0639 d and a period of 51.5 yr. After the long-term period increase and the large-amplitude period oscillation were subtracted from the O-C curve, the residuals of the photoelectric and CCD data indicate a small-amplitude cyclic variation with a period of 8.75 yr and a small amplitude of 0.0048 d. The continuous period increase indicates a conservative mass transfer at a rate of dM2/dt = 7.89 × 10^-8 M⊙ yr^-1 from the secondary to the primary. The period increase may be caused by a combination of the mass transfer from the secondary to the primary and the angular momentum transfer from the binary system to the circumbinary disk. The two cyclic period oscillations can be explained by light-travel time effects via the presence of additional bodies. The small-amplitude periodic change indicates the existence of a less massive component with mass M3 〉 0.53 M⊙, while the large-amplitude one is caused by the presence of a more massive component with mass M4 〉 2.84M⊙. The ultraviolet source in the system reported by Kviz ＆ Rufener （1987） may be one of the additional components, and it is possible that the more massive one may be an unseen neutron star or black hole. The rapid period increase and the possibility of the presence of two additional components in the binary make it a very interesting system to study. New photometric and high-resolution spectroscopic observations and a detailed investigation of those data are required in the future.