Damping rates of solar-like oscillations across the HR diagram

Theoretical calculations confronted to CoRoT and Kepler observations

¹ LESIA, UMR8109, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195 Meudon Cedex, France
e-mail: kevin.belkacem@obspm.fr
² Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium
³ Institut d’Astrophysique Spatiale, CNRS, Université Paris XI, 91405 Orsay Cedex, France
⁴ Georg-August-Universität Göttingen, Institut für Astrophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Received: 26 January 2012
Accepted: 7 March 2012

Abstract

The space-borne missions CoRoT and Kepler are providing a rich harvest of high-quality constraints on solar-like pulsators. Among the seismic parameters, mode damping rates remains poorly understood and are thus barely used to infer the physical properties of stars. Nevertheless, thanks to the CoRoT and Kepler spacecrafts it is now possible to measure damping rates for hundreds of main-sequence and thousands of red-giant stars with unprecedented precision. By using a non-adiabatic pulsation code including a time-dependent convection treatment, we compute damping rates for stellar models that are representative of solar-like pulsators from the main-sequence to the red-giant phase. This allows us to reproduce the observations of both CoRoT and Kepler, which validates our modeling of mode damping rates and thus the underlying physical mechanisms included in the modeling. By considering the perturbations of turbulent pressure and entropy (including the perturbation of the dissipation rate of turbulent energy into heat) by the oscillation in our computation, we succeed in reproducing the observed relation between damping rates and effective temperature. Moreover, we discuss the physical reasons for mode damping rates to scale with effective temperature, as observationally exhibited. Finally, this opens the way for the use of mode damping rates to probe turbulent convection in solar-like stars.