Fission Cycling in a Supernova r-process

TL;DR

This paper investigates how fission cycling and steady-beta flow influence the r-process nucleosynthesis in supernova neutrino-driven winds, aiming to explain observed abundance patterns between the second and third peaks.

Contribution

It analyzes the conditions under which fission cycling and steady-beta flow occur in supernova environments, proposing modifications to neutrino physics to facilitate these mechanisms.

Findings

Fission cycling can produce yields between the second and third r-process peaks.

Steady-beta flow explains consistent abundance patterns across different astrophysical conditions.

Traditional neutrino-driven wind models require modifications to support these mechanisms.

Abstract

Recent halo star abundance observations exhibit an important feature of consequence to the r-process: the presence of a main r-process between the second and third peaks which is consistent among halo stars. We explore fission cycling and steady-beta flow as the driving mechanisms behind this feature. The presence of fission cycling during the r-process can account for nucleosynthesis yields between the second and third peaks, whereas the presence of steady-beta flow can account for consistent r-process patterns, robust under small variations in astrophysical conditions. We employ the neutrino-driven wind of the core-collapse supernova to examine fission cycling and steady-beta flow in the r-process. As the traditional neutrino-driven wind model does not produce the required very neutron-rich conditions for these mechanisms, we examine changes to the neutrino physics necessary for fission cycling to occur in the neutrino-driven wind environment, and we explore under what conditions steady-beta flow is obtained.