Constraining the difference in convective blueshift between the components of α Centauri with precise radial velocities

¹ Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, C.P. 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
² Department of Astrophysical Sciences, Princeton University, Princeton NJ 08544-1001, USA
³ Department of Physics and Astronomy, San Francisco State University, CA 94132, USA
⁴ Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington DC 20015-1305, USA
⁵ Anglo–Australian Observatory, PO Box 296, Epping, NSW 1710, Australia
⁶ Department of Astronomy, University of California, Berkeley, CA 94720, USA
⁷ Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf Birkenhead CH41 1LD, UK
⁸ Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK
⁹ Faculty of Sciences, University of Southern Queensland, Toowoomba, 4350, Australia
¹⁰ Observatoire de Genève, 1290 Sauvergny, Switzerland
¹¹ Mount John University Observatory, Department of Physics and Astronomy, University of Canterbury, Orivate Bag 4800, Christchurch, New Zealand

Corresponding author: D. Pourbaix, pourbaix@astro.ulb.ac.be

Received: 13 December 2001
Accepted: 20 February 2002

Abstract

New radial velocities of α Cen A & B obtained in the framework the Anglo-Australian Planet Search programme as well as in the CORALIE programme are added to those by Endl et al. ([CITE]) to improve the precision of the orbital parameters. The resulting masses are   and   for A and B respectively. The factors limiting how accurately these masses can be derived from a combined visual-spectroscopic solution are investigated. The total effect of the convective blueshift and the gravitational redshift is also investigated and estimated to differ by m s^-1 between the components. This suggests that the difference in convective blueshift between the components is much smaller than predicted from current hydrodynamical model atmosphere calculations.