β Centauri: An eccentric binary with two β Cep-type components^*

¹ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium
² Space Department, TNO TPD, Stieltjesweg 1, 2600 AD Delft, The Netherlands
³ Koninklijke Sterrenwacht van België, Ringlaan 3, 1080 Brussels, Belgium

Corresponding author: C. Aerts, conny@ster.kuleuven.ac.be

Received: 21 December 2001
Accepted: 2 January 2002

Abstract

We introduce our observational study of the orbital motion and the intrinsic variability of the double-lined spectroscopic binary β Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of β Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of β Cen and find a very eccentric orbit () and similar component masses with a mass ratio . Cen forms a challenge for current evolution scenarios in close binaries and it is also a puzzle how a massive binary with such a large eccentricity could have formed in the first place. Both the primary and the secondary exhibit line-profile variations. A period analysis performed on the radial velocity variations of the primary after prewhitening the orbital motion leads to the detection of at least 3 pulsation frequencies while the star does not show any periodic photometric variability.