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The impact of differential rotation on gravito-inertial modes and applications to fast-rotating stars.
Giovanni Mirouh (IRAP / OMP), Jérôme Ballot (IRAP/OMP), Clément Baruteau (IRAP/OMP), Michel Rieutord (IRAP/OMP)
While slowly rotating stars are well described through asteroseismology, Kepler data show that the oscillation spectra of fast differentially rotating stars are much more complicated. The interpretation of such spectra typically requires an expensive forward-modelling approach and a good understanding of mode properties. Using a simplified model, we studied the effects of a differential rotation on the low-frequency spectrum of fast rotating stars, which corresponds to gravito-inertial modes probing the deep layers of the stellar radiative zone. We solve the oscillation problem (i) by computing the paths of characteristics in the non-dissipative limit and (ii) by solving the fully-dissipative eigenproblem numerically. I will present how the non-dissipative study allows us to determine the frequency range in which gravito-inertial modes can exist, predict the extent of the propagation domain, the appearance of attractors, wedge trapping, or critical layers. The simulations give us scaling laws for the damping rates, unveil modes unstable to baroclinic instabilities, and show the existence of quasi-regular modes. I will finally discuss how the results of this study give diagnostics that can be applied to more realistic models of rapidly and differentially rotating stars, and lead to accurate mode identification.