Non standard s-process in massive rotating stars. Yields of $10-150$ $M_{\odot }$ models at $Z=10^{-3}$

Abstract

Recent studies show that rotation significantly affects the s-process in massive stars. We provide tables of yields for non-rotating and rotating massive stars between 10 and 150 $M_{\odot }$ 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. A grid of stellar models with initial masses of 10, 15, 20, 25, 40, 60, 85, 120 and 150 $M_{\odot }$ 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 ${}^{17}$O($\hat{I}\pm ,{\hat{I}}^3$) reaction rate. At the considered metallicity, rotation has a strong impact on the production of s-elements for initial masses between 20 and 60 $M_{\odot }$. In this range, the first s-process peak is boosted by $2-3$ dex if rotation is included. Above 60 $M_{\odot }$, 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 $40\lesssim Z\lesssim 60$ elements by $\sim 0.5-1$ dex. Adopting a reasonably lower ${}^{17}$O($\hat{I}\pm ,{\hat{I}}^3$) rate in the fast rotating model (70$\%$ of the critical velocity) boosts again the yields of s-elements with $55\lesssim Z\lesssim 82$ 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.

16 pages, 14 figures, 4 tables. Accepted for publication in A&A