Significant discrepancies between stellar evolution models and solar-type eclipsing and visual binaries ?

E. LastennetDepto. de Astronomia, UFRJ, Rio de Janeiro, BrazilJ. FernandesObservato´rio Astrono´mico da Univ. de Coimbra, PortugalE. OblakObservatoire de Besancon, UMR CNRS 6091, FranceD. Valls-GabaudUMR CNRS 5572, Observatoire Midi-Pyren´ees, Toulouse, FranceAbstract. Individual components of well-detached binary systems areassumed to be two single-like stars with a common origin, i.e. they sharethe same chemical composition and same age. Therefore, one expects tofit the observed parameters of both components with a single isochrone atthe same metallicity. We show that serious problems appear for systemswith accurate fundamental data (eclipsing binaries in the field and in theHyades, and a visual binary) in the 0.7-1.1 M