The evolutionary state of contact and near-contact binary stars

A compilation is presented of the masses, radii and luminosities of the components of 31 F-K type binary systems which have been found to be in contact or near-contact states. Comparisons of these data with those expected for single stars demonstrate that (i) the primary components of the shallow-contact W-type WUMa systems are unevolved main-sequence stars whilst those of the deeper-contact A-type systems are near to the terminal-age main sequence, (ii) the secondary components of the W-type systems have radii of the order of 1.5 times larger than expected for their ZAMS masses whilst those of the A-type systems have radii of the order of three times larger, (iii) the nine systems in the sample which do not display EW-type light curves can be divided into three groups: three marginal-contact systems, five semi-detached systems, and one detached system. (author)