Calculation of tidal-evolution constants for close binary systems

Tidal torque constants are calculated for each component of 112 close eclipsing binaries of the DMS type (detached components located within the main sequence) from the catalogue by Svechnikov and Perevozkina (1999) on the basis of the evolutionary models by Claret (2004), which are the first to present constants for investigation of tidal effects in close binaries. This study applies conversion of a grid of model tracks into that of isochrones with an arbitrarily small time step based on optimal nonlinear interpolation. The small time-step criterion guarantees application of the linear interpolation procedure to estimate the age of the DMS components and find an individual set of tidal-evolution constants for the close binary under study that refers to the estimated time point. The theoretical values of the apsidal motion period calculated from the individual internal structure constants for each close binary are well consistent with the observations. This confirms the validity of the evolutionary stellar models by Claret and the numerical algorithm proposed here.