Taking into account radiative acceleration we have reexamined the condition for critical rotation. The latter is found to be identical with its classical counterpart, whereas the Eddington luminosity for rigidly rotating objects turns out to be reduced by up to per cent by rotation in the critical case. The existence of an "-limit" claimed in previous investigations is shown to be an artifact of disregarding the effect of gravity darkening. Thus, even if the bipolar structure of LBV nebulae suggests that rotation is a major ingredient in LBV eruptions, the conclusion that the -limit is involved here (Langer 1997) cannot hold.
As a consequence of our study, rotation-dependent mass loss rates involving the -limit which were adopted in recent stellar evolution calculations are unfounded. Estimating the line-driven mass loss rate on the basis of the scaling laws of the CAK theory we find its dependence on rotation to be rather weak. In particular, it never diverges due to the influence of rotation. Given these results, it seems unlikely that the dependence on rotation of stellar mass loss rates will have significant consequences for stellar evolution.
© European Southern Observatory (ESO) 1998
Online publication: September 30, 1998