Further critical tests of stellar evolution by means of double-lined eclipsing binaries

Abstract

The most accurately measured stellar masses and radii come from detached, double-lined eclipsing binaries, as compiled by Andersen. We present a detailed quantitative comparison of these fundamental data with evolution models for single stars computed with our evolution code, both with and without the effects of enhanced mixing or overshooting beyond the convective cores. We use the same prescription for overshooting that Schröder, Pols & Eggleton found to reproduce the properties of ö Aurigae binaries. For about 80 per cent of the 49 binary systems in the sample, both sets of models provide a good fit to both stars at a single age and metallicity within the observational uncertainties. We discuss possible causes for the discrepancies in the other systems. For only one system, AI Hya, do the enhanced-mixing models provide a significantly better fit to the data. For two others (WX Cep and TZ For) the fit to the enhanced-mixing models is also better. None of the other systems can individually distinguish between the models with and without enhanced mixing. However, the number of systems in a post-main-sequence phase is in much better agreement with the enhanced-mixing models. This test provides supportive evidence for extended mixing in main-sequence stars in the range 2–3 M⊙.