Non-adiabatic analysis of low-frequency oscillations of uniformly rotating stars

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Abstract
Solving linear differential equations of fully non-adiabatic non-radial oscillations, we examined the stability of low-frequency oscillations of uniformly rotating massive main-sequence stars. We found that the dynamically overstable convective modes coupled with higher order g modes in the envelope remain overstable in the full non-adiabatic analysis. The amplitude of such mixed-mode oscillations is large both in the core and in the envelope. This result supports the suggestion based on an adiabatic analysis that such mixed-mode oscillations are responsible for the oscillations in the variable B stars. Some convective (inertial) modes which are purely oscillatory under the adiabatic assumption due to the stabilization of rotation become unstable when non-adiabatic effects are included. Such modes are totally confined in the convective core and hence not observable on the surface. Gravity modes and rotational modes are all stabilized by the radiative dissipation in the envelope. When they are coupled with oscillatory convective (inertial) modes in the core, the damping rates of modes are largely reduced, because a large part of the kinetic energy is confined into the core where non-adiabatic effects are small.

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