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Diagnostics sismiques des intérieurs stellaires avec Kepler : rotation et interfaces

Abstract : Asteroseismology, the study of stellar oscillations, provides a direct way to probe the physics of stellar interiors. With four years of seismic data of unprecedented quality, the Kepler mission allows us to test stellar structure and evolution models on fields that were out of reach before. In a first part, I broach the problem of rotation and angular momentum transport in stars with a novel viewpoint : that of γ Doradus pulsators. Seismic studies of the Sun and red giants revealed that one or several transport mecanisms are missing in current stellar evolution models. As progenitors of redgiants, γ Dor stars are of particular interest but they are also moderate to rapid rotators for which an appropriate treatment of the rotation-pulsation coupling is needed. This led to the development of morse , a diagnostic tool for mode identification and the measurements of the internal rotation rates of γ Dors. After ensuring the reliability of this tool, I measured the internal rotation rates of 36 γ Dors observed by Kepler . A first comparison of these measurements with CESTAM models that include transport by meridional circulation and shear turbulence, shows that a supplementary transport is extracting angular momentum from the core of these stars. This mechanism remains to be identified. In the second part, I started a systematic seismic study of the phenomenon of penetrative convection occuring at the interface of the convective envelope and radiative interior of solar-like stars. The seismic signature of the base of the convective envelope is used to calibrate the size of the penetration region on the basis of the model proposed by Zahn (1991). Preliminary results obtained for two solar-like pulsators of the Kepler legacy sample suggest that the size of this zone is weakly dependent on stellar age, metallicity or mass.
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Submitted on : Monday, June 29, 2020 - 3:43:46 PM
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  • HAL Id : tel-02883979, version 1


Steven Christophe. Diagnostics sismiques des intérieurs stellaires avec Kepler : rotation et interfaces. Astrophysique [astro-ph]. Université Paris sciences et lettres, 2019. Français. ⟨NNT : 2019PSLEO011⟩. ⟨tel-02883979⟩



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