Non-standard s-process in massive rotating stars

Yields of 10–150 M_⊙ models at Z = 10^−3⋆

¹ Geneva Observatory, University of Geneva, Maillettes 51, 1290 Sauverny, Switzerland
e-mail: arthur.choplin@unige.ch
² Astrophysics Group, Lennard-Jones Labs 2.09, Keele University, ST5 5BG, Staffordshire, UK
³ Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, 5-1-5 Kashiwanoha, 277-8583 Kashiwa, Japan
⁴ UK Network for Bridging the Disciplines of Galactic Chemical Evolution (BRIDGCE), UK
⁵ Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁶ Department of Physics, University of York, YO10 5DD York, UK

Received: 23 April 2018
Accepted: 18 July 2018

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(α, γ) 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(α, γ) 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.