CoRoT Symposium 3, Kepler KASC-7 joint meeting
6-11 Jul 2014 Toulouse (France)

Abstracts > Grosjean Mathieu

Non-adiabatic study of Kepler subgiants
Mathieu Grosjean  1@  , Marc-Antoine Dupret  1@  , Kevin Belkacem  2  , Reza Samadi  2  
1 : Département d'astrophysique, Géophysique et Océanographie  (AGO)  -  Website
17 Allée du 6 Août 4000 Sart-Tilman -  Belgium
2 : Laboratoire d'études spatiales et d'instrumentation en astrophysique  (LESIA)  -  Website
Université Pierre et Marie Curie [UPMC] - Paris VI, Observatoire de Paris, INSU, CNRS : UMR8109, Université Paris VII - Paris Diderot, Université Pierre et Marie Curie (UPMC) - Paris VI
5, place Jules Janssen 92190 MEUDON -  France

Thanks to the precision of CoRoT and Kepler observations, it becomes possible to have access to the detailed structure of solar-like oscillations power spectrum in evolved stars.
Comparisons between the theoretical predictions of our non-adiabatic code with observations give important constraint on red-giants models. Lifetimes and amplitudes of modes trapped in the envelope (e.g. radial modes) constrain the characteristics of the convective envelope and its time-dependent interaction with oscillations. Lifetimes and amplitudes of mixed-modes (mainly dipole modes) strongly depend on mode trapping, allowing us to probe the core of red-giants. 

Benomar et al. (2013) have recently measured the linewidth and amplitude of individual modes (including mixed modes) in several Kepler subgiants. We first model these stars based on surface properties and observed frequencies. For the first time, we perform non-adiabatic computations for particular observed subgiants. These computations include a time-dependant treatment of convection and give the theoretical lifetimes of radial and non-radial modes (including mixed-modes). Next, combining the lifetimes and inertias with a stochastic excitation model gives us the theoretical amplitudes of the modes.

We can now directly compare theoretical and observed linewidths and amplitudes of mixed-modes for some specific stars. This allows us to test the accuracy of our present damping and excitation models in evolved stars and especially the interaction between convection and oscillations.


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