The importance of charged particle reactions in the r-process on supernovae and neutron stars

TL;DR

This paper introduces a new nuclear reaction mechanism involving charged particles that could explain the synthesis of heavy elements and actinide abundances in supernovae and neutron star environments, challenging previous assumptions about extreme nuclear conditions.

Contribution

It proposes a novel $(p,xn)$ reaction mechanism that extends the rp-process and explains observed heavy element and actinide abundances without requiring extreme nuclear drip line conditions.

Findings

The proposed mechanism can produce thorium and uranium compatible with stellar conditions.

Charged particle reactions can account for discrepancies in nucleochronometers.

The extended rp-process contributes to heavy stable neutron-deficient nuclide synthesis.

Abstract

We propose a $(p,xn)$ mechanism with dynamic production as a new set of nuclear reactions that could produce high density neutrons and explain the r- and rp-elements. We calculate the rate of thorium and uranium produced by our proposed mechanism and show that it is compatible with different stellar conditions found in explosive events at an initial temperature of $T \geq 3\times 10^{9} K$ with a "freeze-out" by a neutrino-driven wind. We show that charged particle reactions could explain the discrepancies in the abundances of ${}^{232}Th$ and ${}^{235,238}U$ nucleochronometers. We extend the endpoint of the rapid proton (rp) process far beyond the previous work by showing that $(p,xn)$ reactions could contribute to the nucleosynthesis of heavy stable neutron deficient nuclides, like ${}^{190}Pt$, ${}^{184}Os$, ${}^{180}W$ and ${}^{174}$Hf. This implies in a broader definition of the rp-process and has important consequences for the nucleosynthesis of heavy elements. We show that we did not need to assume an extreme condition for the drip line of super neutron-rich nuclei.