Detailed models of \alpha Cen A and B based on new seismological data for \alpha Cen B by Carrier & Bourban ( [ ] ) have been computed using the Geneva evolution code including atomic diffusion .
Taking into account the numerous observational constraints now available for the \alpha Cen system , we find a stellar model which is in good agreement with the astrometric , photometric , spectroscopic and asteroseismic data .
The global parameters of the \alpha Cen system are now firmly constrained to an age of t = 6.52 \pm 0.30 Gyr , an initial helium mass fraction Y _ { \mathrm { i } } = 0.275 \pm 0.010 and an initial metallicity ( Z / X ) _ { \mathrm { i } } = 0.0434 \pm 0.0020 .
Thanks to these numerous observational constraints , we confirm that the mixing–length parameter \alpha of the B component is larger than the one of the A component , as already suggested by many authors ( Noels et al . [ ] , Fernandes & Neuforge [ ] and Guenther & Demarque [ ] ) : \alpha _ { \mathrm { B } } is about 8 % larger than \alpha _ { \mathrm { A } } ( \alpha _ { \mathrm { A } } = 1.83 \pm 0.10 
and \alpha _ { \mathrm { B } } = 1.97 \pm 0.10 ) .
Moreover , we show that asteroseismic measurements enable to determine the radii of both stars with a very high precision ( errors smaller than 0.3 % ) .
The radii deduced from seismological data are compatible with the new interferometric results of Kervella et al .
( [ ] ) even if they are slightly larger than the interferometric radii ( differences smaller than 1 % ) .