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Issue A&A Volume 392, Number 1, September II 2002 Page(s) 169 - 180 Section Formation, structure and evolution of stars DOI 10.1051/0004-6361:20020934

A&A 392, 169-180 (2002)
DOI: 10.1051/0004-6361:20020934

Convective core mixing: A metallicity dependence?

D. Cordier^{1, 2}, Y. Lebreton¹, M.-J. Goupil¹, T. Lejeune³, J.-P. Beaulieu⁴ and F. Arenou<sup>1

1</sup>  DASGAL, CNRS UMR 8632, Observatoire de Paris-Meudon, DASGAL, 92195 Meudon Principal Cedex, France
²  École Nationale Supérieure de Chimie de Rennes, Campus de Beaulieu, 35700 Rennes, France
³  Observatorio Astronomico, Universidade de Coimbra, Santa Clara 3040 Coimbra, Portugal
⁴  I.A.P., 98bis boulevard Arago, 75014 Paris, France

(Received 5 March (2002) / Accepted 6 June (2002) )

Abstract
The main purpose of this paper is to investigate the possible existence of a metallicity dependence of the overshooting from main sequence star turbulent cores. We focus on objects with masses in the range ~ -~ . Evolutionary time scale ratios are compared with star number ratios on the main sequence. Star populations are synthesized using grids of evolutionary tracks computed with various overshooting amounts. Observational material is provided by the large and homogeneous photometric database of the OGLE 2 project for the Magellanic clouds. Attention is paid to the study of uncertainties: distance modulus, intergalactic and interstellar reddening, IMF slope and average binarity rate. Rotation and the chemical composition gradient are also considered. The result for the overshooting distance is ( Z₀=0.004) and ( Z₀=0.008) suggesting a possible dependence of the extent of the mixed central regions with metallicity within the considered mass range. Unfortunately it is not yet possible to fully disentangle the effects of mass and chemical composition.

Key words: convection -- stars: evolution, interiors

Offprint request: D. Cordier, daniel.cordier@ensc-rennes.fr

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