The nearby eclipsing stellar system δ Velorum

II. First reliable orbit for the eclipsing pair^⋆,⋆⋆

¹ Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergäßchen 2-3, 07745 Jena, Germany
e-mail: alex@astro.uni-jena.de; markus@astro.uni-jena.de
² Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovakia
e-mail: pribulla@ta3.sk; vanko@ta3.sk
³ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
e-mail: amerand@eso.org
⁴ LESIA, Observatoire de Paris, CNRSUMR8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France
e-mail: Pierre.Kervella@obspm.fr
⁵ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
e-mail: irs@star.sr.bham.ac.uk
⁶ Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany
e-mail: chini@astro.rub.de; vhoff@astro.rub.de
⁷ Facultad de Ciencias, Universidad Católica del Norte, Antofagasta, Chile
⁸ ZAH, Landessternwarte Königstuhl, 69117 Heidelberg, Germany
e-mail: o.stahl@lsw.uni-heidelberg.de
⁹ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
e-mail: ammler@mps.mpg.de

Received: 29 November 2010
Accepted: 27 December 2010

Abstract

Context. The nearby multiple system δ Velorum contains a widely detached eclipsing binary and a third component.

Aims. We take advantage of this system offering the opportunity to determine the set of fundamental parameters (masses, luminosities, and radii) of three coeval stars with sufficient precision to test models of stellar evolution.

Methods. Extensive high-resolution spectroscopy is analyzed by the broadening function technique to provide the first spectroscopic orbit of the eclipsing pair. Simultaneous analysis of the spectroscopic data and the SMEI satellite light curve is performed to provide astrophysical parameters for the components. We use a modified Roche model assuming an eccentric orbit and asynchronous rotation.

Results. The observations show that components of the eclipsing pair rotate at about two-thirds of the break-up velocity, which excludes any chemical peculiarity and results in a non-uniform surface brightness. Although the inner orbit is eccentric, no apsidal motion is seen during the SMEI photometric observations. For the inner orbit, the orbital parameters are eccentricity e = 0.290, longitude of the periastron passage ω = 109°, and inclination 89.0°.

Conclusions. The component masses of M_Aa = 2.53 ± 0.11   M_⊙, M_Ab = 2.37 ± 0.10   M_⊙, and M_B ~ 1.5   M_⊙ combined with the inferred radii of the Aa and Ab components indicate that the eclipsing pair has already left the main sequence and that the estimated age of the system is about 400 Myr.