A- and B-type star pulsations in the Kepler and CoRoT era: theoretical considerations

Abstract

Among A-type main-sequence variables, pulsations of $\delta$ Sct and $\gamma$ Dor variables are driven in the He II ionization zone, while H-ionization zone and strong magnetic fields seem to play roles in the excitation of high-order p-modes in rapidly oscillating Ap (roAp) stars. Pulsations in B-type variables, $\beta$ Cephei and slowly pulsating B (SPB) stars are excited by the $\kappa$-mechanism at the Fe-opacity bump at $T\approx 2\times10^5$K. In addition, the strange-mode instability seems responsible for the excitation of pulsations in luminous AB-supergiants ($\alpha$ Cygni variables). We discuss excitation mechanisms for pulsations in A- and B-type variables stars.