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Etude des éléments chimiques et tests sismiques de la structure interne du Soleil et des étoiles

Abstract : Stellar physics groups different fields which come from hydrodynamic modelisation to asteroseismology, or abundances observations and extrasolar planets searching. The work presented in this thesis is diversified and is related to several of these fields. It uses computer tools of modelisation such as the TGEC (Toulouse-Geneva Evolution Code) or the adiabatic oscillations code PULSE.

The two first parts of this manuscript present by a theoritical way the transport processes and the principles of asteroseismology used in the stellar models.

The third part is interested by the asteroseismic signature of the helium diffusion in the late F-type stars et by its evolution. We show that the gradient created by the helium diffusion under the convective zone leads to a spike in the Fourier transform of the second differences of the oscillation frequences spectra. The more important is the gradient, the higher is the amplitude of the spike.

The fourth chapter studies the lithium depletion in stars with planet. Recent observations of Israelian et al. (2004) show that the cold stars with planet have an important lithium depletion, contrary to the stars without planet. Our overmetallic models have allowed to show, on the one hand that the $\mu$-gradient could stabilize the mixing in stars without planet, preventing the lithium destruction, and on the other hand that the destruction in stars with planet could come from shearing instabilities due to the planets migration to the central star.

Finally, the fifth part present a work on solar models with the new abundances of Asplund et al. (2005), which show a disagreement with the helioseismic inferrences. Our models simulating an undermetallic accretion at the beginning of the main sequence improve the situation but do not succeed to restore the agreement with helioseismology, despite the introduction of an overshooting and a rotational mixing under the base of the convective zone.
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Submitted on : Wednesday, January 31, 2007 - 10:13:13 AM
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Matthieu Castro. Etude des éléments chimiques et tests sismiques de la structure interne du Soleil et des étoiles. Astrophysique [astro-ph]. Université Paul Sabatier - Toulouse III, 2006. Français. ⟨tel-00128196⟩

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