Radiation Hydrodynamics Simulations of Turbulent Convection for Kepler Target Stars

The solar-type pulsators are characterized by acoustic oscillation modes excited by turbulent granular convection in the upper convective boundary layer. As the stellar mass increases the convection zone shrinks, the scale and intensity of the turbulent motions increases, providing more energy for excitation of acoustic modes. When the stellar mass reaches about 1.6 solar masses the upper convection zone consists of two very thin layers corresponding to H and He ionization, and in addition to the acoustic modes the stars show strong internal gravity modes The thin convection zone is often considered insignificant for the stellar dynamics and variability. We use numerical radiation transfer simulations in three dimensions (3D) to study convective and oscillation properties of main-sequence stars from the solar-type stars to more massive stars. In the simulations we used models of the stellar interior, calculated for individual Kepler mission targets. The 3D radiation hydrodynamics simulations reveal supersonic granular-type convection on a scale significantly larger than the solar granulation, and strong overshooting plumes penetrating into the stable radiative zone, which can affect oscillation properties of a star.