Non-standard s-process in massive rotating stars

Abstract

Context
Recent studies show that rotation significantly affects the s-process in massive stars.

Aims
We provide tables of yields for non-rotating and rotating massive stars between 10 and 150 M? at Z = 10-3 ([Fe/H] = -1.8). Tables for different mass cuts are provided. The complete s-process is followed during the whole evolution with a network of 737 isotopes, from hydrogen to polonium.

Methods
A grid of stellar models with initial masses of 10, 15, 20, 25, 40, 60, 85, 120, and 150 M? and with an initial rotation rate of both 0% or 40% of the critical velocity was computed. Three extra models were computed in order to investigate the effect of faster rotation (70% of the critical velocity) and of a lower 17O(a, ?) reaction rate.

Results
At the considered metallicity, rotation has a strong impact on the production of s-elements for initial masses between 20 and 60 M?. In this range, the first s-process peak is boosted by 2-3 dex if rotation is included. Above 60 M?, s-element yields of rotating and non-rotating models are similar. Increasing the initial rotation from 40% to 70% of the critical velocity enhances the production of 40 ? Z ? 60 elements by ~0.5-1 dex. Adopting a reasonably lower 17O(a, ?) rate in the fast-rotating model (70% of the critical velocity) boosts again the yields of s-elements with 55 ? Z ? 82 by about 1 dex. In particular, a modest amount of Pb is produced. Together with s-elements, some light elements (particularly fluorine) are strongly overproduced in rotating models.