Can Extreme Differential Rotation Increase the Core Masses of Upper Main Sequence Stars?
Session 45 -- Early Type Stars
Display presentation, Wednesday, 9:20-6:30, Heller Lounge Room

## [45.03] Can Extreme Differential Rotation Increase the Core Masses of Upper Main Sequence Stars?

M. J. Clement (University of Toronto)

Accurate two-dimensional models of rotating main sequence stars have been computed to test the recently proposed hypothesis that stars with a uniform distribution of specific angular momentum have more massive convective cores and, hence, longer than normal lifetimes relative to their rigidly rotating and nonrotating counterparts. The main conclusion is that these models do, indeed, confirm the hypothesis at least for intermediate mass stars with ${\rm M} < 12\,{\rm M}_{\odot}$. In more massive configurations, the radiative temperature gradient at the core boundary still increases with rotation (as in lower masses) but the adiabatic gradient increases even more due to a drop in the radiation pressure. The result is that the convective cores of rotating massive stars always decrease in mass fraction for any distribution of angular velocity. This phenomenon provides yet another possible explanation for blue stragglers and other peculiar stars that may arise from enhanced core-envelope mixing.