Modeling the activity of late-type stars with spectropolarimetry and photometry

Soutenance de thèse de Tianqi Cang (Salle Coriolis)

Résumé de la thèse :

The various active phenomena observed in solar-type stars are a consequence of their internal magnetism.  During the last three decades, the spectacular progress in our capacity to measure and model the Zeeman effect increased our knowledge of stellar magnetism dramatically.  A fine understanding of stellar activity is also critical to optimize the filtering of activity signatures in searches for exoplanets, and to model the environment of close-in planets. We propose to build a near-infrared CubeSat-type photometer named MARSU to characterize transiting exoplanets and activity-induced brightness variations of the host stars. 
In the first study of this thesis, we investigated the magnetic activity of the prototypical, zero-age main sequence, rapid rotator V530 Per. Using tomography tools, time-resolved spectropolarimetric observations enabled us to explore the surface distribution of brightness and magnetic fields, the latitudinal differential rotation, and the prominence system.  In the second part of the thesis,  we developed an end-to-end numerical simulator of MARSU observations, and confirmed the feasibility to detect transiting Earth-like planets in the habitable zone of M dwarfs, while characterizing the activity of the host star.  

Composition du jury de thèse :

• Gaitee HUSSAIN (European Space Agency — Rapporteure)
• Shenghong GU (Chinese Academy of Sciences Yunnan Observatory — Rapporteur)
• Catherine DOUGADOS (IPAG — Examinatrice)
• Jianning FU (Beijing Normal University — Examinateur)
• Arturo LOPEZ ARISTE (IRAP — Examinateur)
• Pascal PETIT (IRAP — Directeur de thèse)
• Jean-François DONATI  (IRAP — Co-directeur de thèse)