Core properties of α Centauri A using asteroseismology

Context. A set of long and nearly continuous observations of alpha Centauri A should allow us to derive an accurate set of asteroseismic constraints to compare to models, and make inferences on the internal structure of our closest stellar neighbour. Aims. We intend to improve the knowledge of the interior of alpha Centauri A by determining the nature of its core. Methods. We combined the radial velocity time series obtained in May 2001 with three spectrographs in Chile and Australia: CORALIE, UVES, and UCLES. The resulting combined time series has a length of 12.45 days and contains over 10 000 data points and allows to greatly reduce the daily alias peaks in the power spectral window. Results. We detected 44 frequencies that are in good overall agreement with previous studies, and found that 14 of these show possible rotational splittings. New values for the large (Delta nu) and small separations (delta nu(02), delta nu(13)) have been derived. Conclusions. A comparison with stellar models indicates that the asteroseismic constraints determined in this study (namely r(10) and delta nu(13)) allows us to set an upper limit to the amount of convective-core overshooting needed to model stars of mass and metallicity similar to those of alpha Cen A.