EDP Sciences
Free access
Volume 413, Number 1, January I 2004
Page(s) 251 - 256
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20031527

A&A 413, 251-256 (2004)
DOI: 10.1051/0004-6361:20031527

The diameter and evolutionary state of Procyon A

Multi-technique modeling using asteroseismic and interferometric constraints
P. Kervella1, F. Thévenin2, P. Morel2, G. Berthomieu2, P. Bordé3 and J. Provost2

1  European Southern Observatory, Casilla 19001, Vitacura, Santiago 19, Chile
2  Département Cassini, UMR CNRS 6529, Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex 4, France
3  LESIA, Observatoire de Paris-Meudon, 5, place Jules Janssen, 92195 Meudon Cedex, France

(Received 19 May 2003 / Accepted 20 August 2003)

We report the angular diameter measurement obtained with the VINCI/VLTI instrument on the nearby star Procyon A ( $\alpha$ CMi A, F5IV-V), at a relative precision of $\pm $ 0.9%. We obtain a uniform disk angular diameter in the K band of $\theta_{\rm UD} = 5.376\pm0.047$ mas and a limb darkened value of $\theta_{\rm LD} = 5.448\pm0.053$ mas. Together with the HIPPARCOS parallax, this gives a linear diameter of $2.048\pm0.025$ $D_{\odot}$. We use this result in combination with spectroscopic, photometric and asteroseismic constraints to model this star with the CESAM code. One set of modeling parameters that reproduces the observations within their error bars are an age of 2314 Myr, an initial helium mass fraction $Y_{\rm i}=0.301$ and an initial mass ratio of heavy elements to hydrogen $(\frac ZX)_{\rm i}=0.0314$. We also computed the adiabatic oscillation spectrum of our model of Procyon A, giving a mean large frequency separation of $\overline{\Delta\nu_0}\approx 54.7\,\mu$Hz. This value is in agreement with the seismic observations by Martic et al. (1999, 2001). The interferometric diameter and the asteroseismic large frequency spacing together suggest a mass closer to 1.4 $M_{\odot}$ than to 1.5 $M_{\odot}$. We conclude that Procyon is currently ending its life on the main sequence, as its luminosity class indicates.

Key words: stars: individual: $\alpha$ CMi -- stars: fundamental parameters -- stars: evolution -- techniques: interferometric

Offprint request: P. Kervella, Pierre.Kervella@eso.org

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