Traditional Approximation for Low-Frequency Modes in Rotating Stars and A Working Hypothesis About Episodic Mass Loss in Be Stars

摘要

The so-called traditional approximation is reasonably good for very low frequency modes of rotating stars. In this approximation, the angular dependence of eigenfunction is expressed in terms of the Hough functions, and the radial dependence is expressed in a form similar to the case of non-rotating stars with only the replacement of the spherical degree with the eigenvalue of the Hough function. Paying attention to the non-zero surface temperature, we point out that very low frequency oscillations become leaky waves. A working hypothesis is then proposed to explain mass loss in Be stars as episodic wave leakage associated with gradual angular-momentum transport due to prograde modes.