ON THE STABILITY AND PULSATIONS OF WOLF-RAYET STARS

Motivated by the discovery of fast pulsations in a Wolf-Rayet star, models of helium main-sequence stars are tested for stability with respect to radial perturbations. Dynamical strange-mode instabilities are identified, in addition to the instability of the fundamental mode driven by the classical epsilon-mechanism and discussed in recent publications. With respect to both range and strength, instabilities caused by the epsilon-mechanism are negligible when compared with strange-mode instabilities. The implication of these results for the interpretation of the observed variability in Wolf-Rayet stars is discussed, in particular with respect to mode identification and mass determinations.