Elliptical motions of stars in close binary systems

The motion of stars in close binary systems with conservative mass transfer is considered. It is shown that the Paczynski-Huang model that is currently used to determine the variations of the semimajor axis of the relative orbit of the stars is not correct, and leads to large errors in the derived semi-major axis. A new model is proposed, suitable for elliptical stellar orbits. The reaction forces and gravitational forces between the stars and the stream of overflowing matter are taken into account. The possibility of mass transfer in the presence of an accretion disk is considered.