## 3. Rotation and mass lossWe have shown in the previous Section that the concept of the
limit is a consequence of omitting the effect of
gravity darkening. As soon as the latter is taken into account the
classical condition for critical rotation remains unaffected. Thus,
any rotation dependent mass loss rate based on the
limit (Langer 1997, 1998) is inconclusive. In
particular, the mass loss rate does not diverge at the
limit, which therefore has no meaning for
stellar evolution. Accordingly, if the mass loss rate depends on
rotation, it should rather be determined by the difference of the
actual and the The dependence on rotation of line-driven mass flux was studied by Friend & Abbott (1986). They ignored gravity darkening and the analysis was restricted to considering the equatorial plane. As a result, the mass flux was found to increase with decreasing effective gravity. Taking gravity darkening into account, however, the opposite dependence on effective gravity is obtained which was pointed out by Owocki et al. (1996) and Owocki & Gayley (1997) on the basis of the scaling laws for the mass flux in the standard CAK theory (Castor et al. 1975). On the same level of approximation as Owocki et al. (1996) we find for the dependence on rotation of the mass flux by using Eqs. (4) and (8): being the usual CAK exponent. We note that
in this estimate the role of centrifugal support is even
overestimated. Eq. (14) is identical to the result of Owocki et al.
(1996) apart from the factor containing
© European Southern Observatory (ESO) 1998 Online publication: September 30, 1998 |