Orbital Period Variations And Photometric Studies Of The Shallow Contact Binary V0339 Com And PV Com

Shallow contact binary is a kind of close binary system with a degree of contact less than 0.2.According to the evolution theory of close binary stars,it happens to be in the marginal state of connection,which is the link between detached or semi-detached binaries and contact one.Because of its specific evolution stage,the study of photometric and period investigation about shallow contact binaries is of great theoretical significance for understanding the evolution of contact binaries and the evolution chain of close binaries.In this thesis,observation,photometric study and orbital period investigation of two shallow contact binary systems V0339 Com and PV Com are studied.The main research contents and results are as follows:1.Using the 60 cm telescope of the National Astronomical Observatory,we made multi-band observations of shallow contact binary V0339 com and PV Com,obtained the light curve of BVR bands.The obvious asymmetry light curves was found(O’Connell effect).Analyzed the multi-band light curve with Wilson-devinney program,results suggested that V0339 Com is A subtype shallow contact binary with degree of contact of 12.0%,The photometric mass ratio is 0.304;PV Com is a W subtype shallow contact binary with degree of contact of 1.9% with the a mass ratio of3.30.The O’Connell effect shown in the light curves of two shallow connected binaries,V0339 com and PV com,is caused by the low-temperature spot activity on the secondary star and the high-temperature spot activity on the secondary star,respectively.2.Based on 179 contact binary samples with reliable physical parameters(94A-subtype contact binaries and 85 W-subtype contact binaries,physical parameters of these contact binaries are determined by the composite solution of light curve and radial velocity curve),we have established a contact binary catalog,deduced an empirical relationship between orbit periods and physical parameters,and determined the absolute physical parameters of V0339 Com and PV Com by using this empirical relationship.Through this empirical relationship,we can determine the parameters of binary system with sky survey data quickly.3.Studied the orbital period of V0339 com and PV com by analyzing the minimum time.We found that the orbital period of V0339 Com is increasing with a continuing rate of P =5.45×10-7d·yr-1,PV Com is reducing with a continuing rate of P =2.50×10-6d·yr-1.We judged that the main cause of the cycle variation is the material transfer between the two components.4.Combined with mass transfer,orbital period change and Roche model,we analyzed the evolution state of V0339 com and PV com.It is found that these two shallow connected binaries are in the edge state predicted by thermal relaxation oscillation theory.Moreover,V0339 com and PV com will evolve from the current shallow connection state to the separate connection state.