SIMBAD references

Detailed models of α Cen A and B based on new seismological data for α Cen B by Carrier & Bourban (2003A&A...406L..23C) have been computed using the Geneva evolution code including atomic diffusion. Taking into account the numerous observational constraints now available for the α 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 α Cen system are now firmly constrained to an age of t=6.52±0.30Gyr, an initial helium mass fraction Y_i=0.275±0.010 and an initial metallicity (Z/X)_i=0.0434±0.0020. Thanks to these numerous observational constraints, we confirm that the mixing-length parameter α of the B component is larger than the one of the A component, as already suggested by many authors (Noels et al., 1991A&A...247..247N; Fernandes & Neuforge, 1995A&A...295..678F; Guenther & Demarque, 2000ApJ...531..503G): α_B is about 8% larger than α_A (α_A=1.83±0.10 and α_B=1.97±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. (2003A&A...404.1087K) even if they are slightly larger than the interferometric radii (differences smaller than 1%).