Light Curve Analysis and Period Study of Two Eclipsing Binaries UZ Lyr and BR Cyg

Abstract Two eclipsing binary systems, UZ Lyr and BR Cyg, are semi-detached types whose secondary component fills its Roche lobe. Although radial velocity and light curves of these systems have already been investigated separately, both their radial velocity and light curves are analyzed simultaneously for the first time in the present study. Also, the orbital period changes of these systems are studied. Our results show that the mass transfers between components have negligible effects on the orbital period changes of these systems, but two light travel time effects are the reasons for the periodic behavior of the O − C curve for UZ Lyr. We could not remark more information about orbital period changes for BR Cyg, but we find a new orbital period for it. By radial velocity and light curve analysis, we find a cold spot on the secondary component of BR Cyg. The new geometrical and physical parameters of both systems are obtained and their positions on the H-R diagram are demonstrated.