Calibrations ofCen A & B

Detailed evolutionary models of the visual bi- nary αCentauri, including pre main-sequence evolution, have been performed using the masses recently deter- mined by Pourbaix et al. (1999). Models have been con- structed using the CEFF equation of state, OPAL opac- ities, NACRE thermonuclear reaction rates and micro- scopic diffusion. A χ2-minimization is performed to de- rive the most reliable set of modeling parameters ℘ = {tαCen, Yi,(Fe H )i, αA, αB}, where tαCen is the age of the sys- tem, Yi the initial helium content, (Fe H )i the initial metal- licity and, αA and αB the convection parameters of the two components. Using the basic Bohm-Vitense (1958) mixing-length theory of convection, we derive ℘BV = {2710Myr,0.284,0.257,1.53,1.57}. We obtain a notice- ably smaller age than estimated previously, in agree- ment with Pourbaix et al. (1999), mainly because of the larger masses. If convective core overshoot is considered we get ℘ov = {3530Myr,0.279,0.264,1.64,1.66}. The use of Canuto & Mazitelli (1991, 1992) convection theory leads to the set ℘CM = {4086Myr,0.271,0.264,0.964,0.986}. Using the observational constraints adopted by Guenther & Demarque (2000), and the basic mixing-length theory, we obtain ℘GD = {5640Myr,0.300,0.296,1.86,1.97} and surface lithium depletions close to their observed values. A seismological analysis of our calibrated models has been performed. The determination of large and small spacings between the frequencies of acoustic oscillations from seismic observations would help to discriminate be- tween the models of αCen computed with different masses and to confirm or rules out the new determination of masses.