ON THE ORBITAL PERIOD CHANGES IN CONTACT BINARIES

Period changes of such complex structures as contact binaries, are connected with the action of individual physical mechanisms and the stability properties of these systems. In order to get information about these processes, we present a new simple method which can give us the observed values of a period and its rate of change for any cycle E, if an O - C diagram is given. Due to their strong coupling, any period variation in a contact binary implies underlying geometrical and structural changes, which can be described mathematically through a system of four differential equations. The equations are developed on the assumption of conservation of total mass and total angular momentum. Their solution can give us (among other quantities) the required rate of mass transfer between components, in order to satisfy the common equipotential surface condition, at any time.