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Évolution de la rotation des étoiles jeunes de faible masse

Abstract : The angular momentum content of a star, as its mass or its chemical composition is one of the fundamental properties of a star, one of those that evolves with time and modify the stellar structure. The angular momentum can be studied as a global property, we can then observe it through the surface rotation velocity, or a local property that vary inside the star, we therefore have to probe the stellar radiation zone and study the secular angular momentum redistribution processes that happen in this region. During this PhD, in the frame of the ToUpiES project, we have been especially interested in the evolution of the young low-mass stars angular momentum, since this phase of evolution is critical regarding the evolution of extraction and redistribution angular momentum processes. First, we included in the STAREVOL evolution code the most up-to-date prescription for the wind-driven angular momentum extraction. We led a systematic study of the various combination of this braking with the different existing prescriptions for the treatment of horizontal and vertical turbulent motions in stellar radiative zones. This allows us to select a set of prescription able to reproduce the observed rotation periods in young open clusters for a broad mass-range. Next, we analysed how these prescriptions for extraction and transport of angular momentum behave when applied to a 1.2M⊙ model. We compared the result to what is obtained with other processes estimated as potentially very efficient to redistribute angular momentum (internal gravity waves, MHD Tayler-Spruit instability, gravity modes). This allows us to derive in each case, the specificity of the rotation profiles predicted by the different transport processes. Then, we set up a functional rotational model adapted to almost the entire range low-mass stars, allowing to reproduce the observed low-mass stars rotation periods in young open clusters (with 0, 2M⊙ ≤M≤ 1, 1M⊙). This models can also predict the rotational evolution at different metallicities. Eventually, these models have been used in the frame of various works in different domains such as the characterisation of planet host-stars, the evolution of the magnetic topology during the young stellar phases or even the impact of stellar evolution on the habitability of a planetary system.
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Submitted on : Friday, June 15, 2018 - 10:31:37 PM
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  • HAL Id : tel-01816982, version 1

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Louis Amard. Évolution de la rotation des étoiles jeunes de faible masse. Astrophysique stellaire et solaire [astro-ph.SR]. Université Montpellier; Observatoire de Genève (Suisse), 2016. Français. ⟨NNT : 2016MONTT258⟩. ⟨tel-01816982⟩

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