Core properties of α Centauri A using asteroseismology

¹ Institut d’Astrophysique et de Géophysique de l’Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium
e-mail: miglio@astro.ulg.ac.be; eggenberger@astro.ulg.ac.be; montalban@astro.ulg.ac.be
² Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
e-mail: fabien@ster.kuleuven.be
³ Sydney Institute for Astronomy (SIfA), School of Physics A28, University of Sydney, NSW 2006, Australia
e-mail: Bedding@physics.usyd.edu.au
⁴ Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
e-mail: hans@phys.au.dk; campante]@phys.au.dk
⁵ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
⁶ Observatoire de Genève, Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland

Received: 10 May 2010
Accepted: 14 July 2010

Abstract

Context. A set of long and nearly continuous observations of α 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 α 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 (Δν) and small separations (δν₀₂, δν₁₃) have been derived.

Conclusions. A comparison with stellar models indicates that the asteroseismic constraints determined in this study (namely r₁₀ and δν₁₃) 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 α Cen A.