Apsidal motion in eclipsing binary systems

A review of work devoted to the problem of apsidal motion in eclipsing binary systems (EBSs) is given. It is shown that recent theoretical models for stars in the main sequence in general are in agreement with the observed apsidal motion velocities. However, the stars of types I–III show more central condensation than predicted by the theoretical models. It is revealed that the observed rates of the stellar photospheric rotation poorly reflect the real rates of axial rotation of greater part of stellar mass (core) and that cores of components of the EBS rotate, on average, more rapidly than their photospheres.