The diameters of α Centauri A and B - A comparison of the asteroseismic and VINCI/VLTI views

P. Kervella; F. Thévenin; D. Ségransan; G. Berthomieu; B. Lopez; P. Morel; J. Provost

doi:10.1051/0004-6361:20030570

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Volume 404 / No 3 (June IV 2003)

A&A, 404 3 (2003) 1087-1097

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Issue		A&A Volume 404, Number 3, June IV 2003


Page(s)		1087 - 1097
Section		Stellar structure and evolution
DOI		https://doi.org/10.1051/0004-6361:20030570
Published online		06 June 2003

A&A 404, 1087-1097 (2003)

The diameters of α Centauri A and B

A comparison of the asteroseismic and VINCI/VLTI views

P. Kervella¹, F. Thévenin², D. Ségransan³, G. Berthomieu², B. Lopez⁴, P. Morel² and J. Provost²

¹ European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile
² Département Cassini, UMR CNRS 6529, Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex 4, France
³ Observatoire de Genève, 1290 Sauverny, Switzerland
⁴ Département Fresnel, UMR CNRS 6528, Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex 4, France

Corresponding author: P. Kervella, pierre.kervella@eso.org

Received: 20 January 2003
Accepted: 9 April 2003

Abstract

We compare the first direct angular diameter measurements obtained on our closest stellar neighbour, α Centauri, to recent model diameters constrained by asteroseismic observations. Using the VINCI instrument installed at ESO's VLT Interferometer (VLTI), the angular diameters of the two main components of the system, α Cen A and B, were measured with a relative precision of 0.2% and 0.6% respectively. Particular care has been taken in the calibration of these measurements, considering that VINCI is estimating the fringe visibility using a broadband K filter. We obtain uniform disk angular diameters for α Cen A and B of $\rm \theta_{\rm UD}[A] = 8.314 \pm 0.016$ mas and $\rm \theta_{\rm UD}[B] = 5.856 \pm 0.027$ mas, and limb darkened angular diameters of $\rm \theta_{\rm LD}[A] = 8.511 \pm 0.020$ mas and $\rm \theta_{\rm LD}[B] = 6.001 \pm 0.034$ mas. Combining these values with the parallax from Söderhjelm (1999), we derive linear diameters of $D[{\rm A}] = 1.224 \pm 0.003\ D_{\odot}$ and $D[{\rm B}] = 0.863 \pm 0.005\ D_{\odot}$ . These values are compatible with the masses published by Thévenin et al. (2002) for both stars.

Key words: techniques: interferometric / stars: binaries: visual / stars: evolution / stars: oscillations / stars: fundamental parameters / stars: individual: α Cen

© ESO, 2003

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