The case of Alpha Centauri - Mass, age and p-mode oscillation spectrum

The authors have investigated the astrometric and physical properties of the α Centauri system, a nearby visual binary which shares a common space motion with the nearest star Proxima Cen. First, the parallax of the binary system is estimated to be 0arcsec.7506±0arcsec.0046 (s.e.). Using this absolute parallax, the masses of α Cen A and B are respectively 1.09±0.01 and 0.90±0.01 M_sun;. Second, the evolutionary status of α Cen A and B is determined with the help of theoretical stellar models. Evolutionary tracks yield the age of the α Cen system as a function of metallicity. The discussion points to a consistent model with an age in the vicinity of 4 - 4.5×109yr. Third, the nonradial oscillations of α Cen A are considered. The p-mode spectrum of the models of α Cen A is compared to that of the Sun and to the observations of Fossat et al. It is concluded that Fossat et al.'s observations are inconsistent with p-mode spectra constructed from standard theoretical models.