Effect of tidal evolution in determining the ages of eclipsing-variable early main sequence close binary systems

Abstract

New Claret evolutionary model-tracks, constructed for the first time for studying close binary systems (CBS) including tidal evolution constants, are used to determine the age of 112 eclipsing-variable stars in the Svechnikov-Perevozkina catalog by the method of isochrones. There is some interest in comparing the calculated ages with previous estimates obtained for these same close binary systems using evolutionary modeltracks for individual stars taking their mass loss into account. A correlation of the ages of the principal and secondary components is noted, which is most marked for massive close binaries with principal components having masses M1 ≥ 3 M⊙. A rejuvenating effect is found to occur for the systems studied here as calculated on the new tracks; it is most distinct for low-mass close binaries with a total mass M1 + M2 ≤ 3.5 M⊙ and is predicted theoretically in terms of magnetic braking. The calculated broadband grid of isochrones, from zero-age main-sequence (ZAMS) to the age of the galaxy, can be used for estimating the ages of close binaries from other catalogs. Ages are given for the 112 eclipsing-variable close binaries with detached components lying within the main sequence.