EDP Sciences
Free access
Issue
A&A
Volume 386, Number 1, April IV 2002
Page(s) 280 - 285
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020287


A&A 386, 280-285 (2002)
DOI: 10.1051/0004-6361:20020287

Constraining the difference in convective blueshift between the components of $\alpha$ Centauri with precise radial velocities

D. Pourbaix1, 2, D. Nidever3, C. McCarthy4, R. P. Butler4, C. G. Tinney5, G. W. Marcy6, H. R. A. Jones7, A. J. Penny8, B. D. Carter9, F. Bouchy10, F. Pepe10, J. B. Hearnshaw11, J. Skuljan11, D. Ramm11 and D. Kent11

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

(Received 13 December 2001 / Accepted 20 February 2002 )

Abstract
New radial velocities of $\alpha$ 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. (2001) to improve the precision of the orbital parameters. The resulting masses are $1.105\pm0.0070$  $M_{\odot}$ and $0.934\pm0.0061$  $M_{\odot}$ 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 $215\,\pm\,8$ 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.


Key words: stars: binaries: general -- stars: individual: $\alpha$ Cen -- methods: data analysis

Offprint request: D. Pourbaix, pourbaix@astro.ulb.ac.be

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