Analysis of α Centauri AB including seismic constraints

¹ Observatoire de Genève, 51 chemin des Maillettes, 1290 Sauverny, Suisse
² Laboratoire d'Astrophysique de Toulouse, CNRS UMR 5572, OMP, 14 Av. E. Belin, 31400 Toulouse, France
³ Département de Physique, Université de Montréal, CP 6128, Station centre-ville, 2900 Bld. Édouard-Montpetit, Montréal PQ H3C 3J7, Canada

Corresponding author: P. Eggenberger, Patrick.Eggenberger@obs.unige.ch

Received: 15 August 2003
Accepted: 6 December 2003

Abstract

Detailed models of α Cen A and B based on new seismological data for α Cen B by Carrier & Bourban ([CITE]) 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  Gyr, an initial helium mass fraction and an initial metallicity . 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. [CITE]; Fernandes & Neuforge [CITE]; Guenther & Demarque [CITE]): is about 8% larger than ( and ). 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. ([CITE]) even if they are slightly larger than the interferometric radii (differences smaller than 1%).