Good Vibrations Seminars S2E5: Sylvain Breton (CEA de Saclay/Université de Paris, France)

November 17, 2021 | 10:00 am 11:00 am

Characterising rotation from the core to the surface in solar-like main-sequence stars 

Sylvain Breton (CEA de Saclay/Université de Paris)

Mechanisms governing angular momentum transport remain one of the main problems to a better understanding of the evolution of main-sequence solar-like stars. Their rotational evolution along the main sequence will remain an open question until we are able to provide reliable observables of both the surface and the core rotation rate for such targets. While p-mode rotational splittings and photometric follow-up of the surface brightness allow independent measurements of stellar rotation rate on the upper regions of these stars and their surface, only g modes are able to provide information about the rotational state of deeper regions. Reliable characterisation of g modes in main-sequence solar-like star would thus be a great step forward concerning our understanding of stellar-interior dynamics. In this talk, I will first describe ROOSTER, a machine learning methodology with ~97% accuracy, designed to reduce the amount of visual inspections when extracting rotation periods from Kepler light curves modulations. I will especially comment on the possibility to compare those results with rotation periods yielded by the analysis of p-mode rotational splittings. Moreover, I will present new perspectives to observe low-degree, low-order solar p modes using the Solar-SONG échelle spectrograph. I will explain how the reduction and analysis I performed on the data collected during the 2018 observational run allows us to improve the SNR below 2 mHz compared to a space instrument like GOLF or a ground-based network like BiSON. I will finally present results from 3D deep-shell hydrodynamical simulations of a F-type star with the ASH code, in which a thin external convective envelope is coupled with the radiative interior. I will show that the differential rotation state of F-type star is different from what is observed in cooler stars. I will then confront the g-mode excitation and visibility at the surface in the simulation with former results obtained for the Sun. Because of the shape of the Brunt-Väisälä profile, the range of excited g modes also significantly differs from what is observed in solar models.  

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