Volume 443, Number 2, November IV 2005
|Page(s)||627 - 641|
|Section||Stellar structure and evolution|
|Published online||04 November 2005|
Helium settling and mass loss in magnetic Ap stars
I. The chemical stratification
Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgique e-mail: Sylvie.Theado@ulg.ac.be
2 Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
3 Laboratoire d'Astrophysique, 14 av. Ed. Belin, 31400 Toulouse, France
Accepted: 4 August 2005
The chemical stratification is likely to play a predominant role in the excitation mechanism of high order modes in rapidly oscillating Ap stars. In this paper we discuss some processes (convection, He settling, mass loss and turbulent mixing) which may strongly affect the chemical composition of Ap stars. We discuss their interplay with a dipolar magnetic field in both magnetic polar and equatorial regions, where the magnetic lines are respectively mainly radially and horizontally oriented. We also present stellar evolutionary computations for magnetic Ap stars. As the magnetic geometry strongly breaks the sphericity of the star, we modeled and computed the polar and equatorial regions separately. We examine the effects of various chemical transport processes on the chemical stratification of both regions. In a forthcoming paper, we will study the stability of these models against pulsations.
Key words: diffusion / stars: abundances / stars: chemically peculiar / stars: interiors / stars: magnetic field / stars: mass loss
© ESO, 2005
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