Observation And Research Of W UMa Type Binary V523 Cas And OT UMa

W UMa-type eclipsing binary refers to a close binary star system composed of two components with a temperature between 4000～8000K filled with their respective Roche lobes,and there is a common envelope around it.The material exchange and magnetic activity between the two components of such binary systems are very frequent.In addition,some binary stars may also be affected by companion stars,which will lead to changes in the orbital period.In order to explore the evolution of such binary stars,we mainly study the evolution of W UMa EBs with a period of around 0.2 days.In this paper,the relevant data of such binary stars are collected,then,two W UMa EBs were selected for observation:The first,we obtained V,R and I bands data by observing V523 Cas,collected all the observed data that have been published at present,and used O-C analysis method to analyze and fit its orbital period changes.The results show that the orbital period of V523 Cas continues to increase,which may be caused by the flow of material from the secondary to the primary.In addition,we consider that the light-travle time effect of the third body causes the system to have a periodic oscillation with a period of 115.24 years,and calculate the parameters（M₃=0.48_?）of the third light.Then,we performed a photometric solutions of V523 Cas using the2015 version of the Wilson-Devinney（W-D）program,and the results showed a clear O’Connell effect,which we thought was caused by cool-spots.And we analyzed that this is a W-subtype binary with a lower temperature of primary than the secondary.In addition,we discussed the evolution of this system,suggested that V523 Cas may be experiencing thermal relaxation oscillations and may develop into more connected evolutionary states in the future.Secondly,we obtained data in the four bands B,V,R_C and I_Cwith OT UMa,and collected all the data that has been published at present.We used the 2015 version of the W-D code to analyze the light curves（LCs）with the best fitting effect of the cool-spot model,and obtained the relevant physical parameters such as mass ratio and effective temperature.Then,the O-C method was used to collect all available light minima times for the first time,and their orbital period changes were studied,resulting in a new linear ephemeris.In addition,the formation and evolution of this binary is discussed,and we considered that OT UMa may also be experiencing thermal relaxation oscillations.