The low mass ratio contact binary system V728 Herculis

Abstract

We present the orbital period study and the photometric analys of the contact binary system V728 Her. Our orbital period analysis shows that the period of the system increases (dP/dt=1.92x10^-7dyr^-1) and the mass transfer rate from the less massive component to more massive one is 2.51x10^-8M_suny^-1. In addition, an advanced sinusoidal variation in period can be attributed to the light-time effect by a tertiary component or the Applegate mechanism triggered by the secondary component. The simultaneous multicolor BVR light and radial velocity curves solution indicates that the physical parameters of the system are M1=1.8M_sun, M2=0.28M_sun, R1=1.87R_sun, R2=0.82R_sun, L1=5.9L_sun, and L2=1.2L_sun. We discuss the evolutionary status and conclude that V728 Her is a deep (f=81%), low mass ratio (q=0.16) contact binary system.Comment: 21 pages, 4 figures, 4 table

Period variation studies of six contact binaries in M4

“…The rate of period changes determined for the variables in the cluster M4 are found to be similar to that observed for the field stars. The secular change could be due to the presence of a tertiary component or to mass transfer or mass loss in the system (Zhang et al 2016, Erkan& Ulas 2016. This can be evaluated through long term variation studies using planned observations with 3.6-m DOT and 4.0-m ILMT at Devasthal Observatory.…”