Influence of a third body on the luminosity of a contact binary system

Abstract

Based on Roche equipotential surface, a theoretical model of contact binary system has been constructed where the system is disturbed by the presence of a third body. Using this model, ratio of the luminosity in the line of sight to the total luminosity has been calculated over the entire cycle of the system as a function of the parameters like mass-ratio q' between masses of the third body and the primary, distance A of the third body from common centre of gravity and angle I between orbital planes of the third body and the binary system. These calculations show a number of anomalous behaviour of the luminosity even at a large distance A = 3 and a small mass ratio q' = 0.1 where phase of the cycle however playa very important role. At higher mass-ratio q' > 0.8, anomaly is still higher. Thus it is suggested that perturbation by a third body can produce anomalous light curve in some contact binary systems.