Impact of rotation and magnetic fields in low mass AGB stars

After core helium burning in low and intermediate-mass stars, starts the AGB phase. In this phase, the s process takes place, which is believed to be at the origin of half of all elements heavier than iron. The role of rotation and magnetic fields on the AGB phase is still debated and uncertain. We have calculated stellar evolution models with MESA for stars with an initial mass of 1.5 and 3.0 solar masses. Our models include both rotation and the Taylor-Spruit (TS) dynamo. We show how these physical processes contribute to the total diffusion coefficient and how it will effect the transport of angular momentum and the s-process nucleosynthesis.

Our preliminary results confirm previous results that inclusion of rotation and the TS dynamo, compared to inclusion of rotation alone, results in an improvement of the predicted rotational period of white dwarfs. Inclusion of the TS dynamo reduces the rotationally induced mixing. The impact on the s-process nucleosynthesis is underway and will be presented in a forthcoming publication. (paper)