ON THE STABILITY AND PULSATIONS OF WOLF-RAYET STARS

Motivated by the discovery of fast pulsations in a Wolf-Rayet star, mo dels of helium main-sequence stars are tested for stability with respe ct to radial perturbations. Dynamical strange-mode instabilities are i dentified, in addition to the instability of the fundamental mode driv en by the classical epsilon-mechanism and discussed in recent publicat ions. 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 part icular with respect to mode identification and mass determinations.