Calibration of the Pre Main Sequence Binary System RS Cha: Impact of the Initial Chemical Mixture

International audienceAccurate observational data are available for the eclipsing double-lined spectroscopic binary system RS Cha composed of two stars in the pre main sequence stage of evolution: masses, radii, luminosities and effective temperatures of each component and metallicity of the system. This allows to build pre main sequence models representing the components of RS Cha and to constrain them in terms of the physical ingredients, initial chemical composition and age. We present stellar models we have calculated with the CESAM code for different sets of physical inputs (opacities, nuclear reaction rates...) and different initial parameters (global metallicity, helium abundance, individual abundances of heavy elements) . We discuss their ability to reproduce the observational constraints simultaneously for the two components. We focus on the impact on the models of the chemical mixture adopted and we propose a calibration for the RS Cha system providing an estimate of its age and initial helium abundance