The Effect of Rotation on Stellar Structure and Evolution

In this thesis, we investigate the eects of rotation on the evolution of stars in the mass range of 2-15 M assuming solar-like initial composition. We have used a well tested hydrodynamical stellar evolution program [El Eid et al., 2009], which has been extended to include a one-dimensional treatment of rotational instabilities. The calculations for stars in the mass range up to 8 M have been performed to include the Asymptotic Giant Branch (AGB) in order to gure out whether rotational instabilities can eect the so called third dredge up , leading to a neutron source for the s-process nucleosynthesis. In the case of massive stars, above 8 M, rotational eects are expected to become important during the main sequence evolution, mainly owing to the so called Eddington-Sweet circulation. An indication of the eect of rotation should show up through the surface enrichment of 4He and 14N at the end of core Hydrogen burning. Another important aspect of rotation is the study of its eect on the shell carbon burning phase, where the s-process nucleosynthesis occurs.[El Eid et al., 2000