## Stellar evolution with rotation## II. A new approach for shear mixing
Recent observations show He- and N-enhancements in fast rotating
O-type stars, while studies on shear mixing in rotating stars have
shown that the This leads us to introduce the following working hypothesis: in a
semiconvection region (or in any zone with other sources of
turbulence) We also examine the coupling of shear mixing and thermal transport;
a third order equation expressing the combined effects is obtained.
The solutions for shears in semiconvective and radiative zones are
examined in detail. The main result of the above developments is the
slight progressive erosion of the In Appendices A and B we rediscuss the diffusion coefficient for semiconvection and find a more general expression, not limited to the adiabatic case.
## Contents- 1. Introduction
- 2. Critical remarks about the current picture of shear mixing
- 3. Partial mixing in a semiconvective shear zone. The diffused fraction
- 4. The thermal adjustment velocity
- 5. The diffusion coefficient for shear mixing
- 6. Coupling the shear mixing and thermal transport
- 7. Discussion of the solutions in radiative shear and semiconvective zones
- 8. Conclusions
- Acknowledgements
- Appendix A
- Appendix A: on the coefficient for semiconvective diffusion by Langer et al.
- Appendix B: derivation of the diffusion coefficient in the mixing-length framework
- References
© European Southern Observatory (ESO) 1997 Online publication: June 30, 1998 |