Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Effect of Finite-Temperature $β$-Decay Rates on the Rapid Neutron Capture Process

Yukiya Saito, Ante Ravlić, Pranav Nalamwar, Rebecca Surman

TL;DR

Finite-temperature $\beta$-decay rates can accelerate the $r$-process flow during the hot early phase and influence freeze-out, with implications for the final abundance pattern and heating. We compute these rates using the FT-PNRQRPA framework, incorporating both allowed and first-forbidden transitions on grids up to $T\sim 10$ GK and $\rho Y_e$ up to $10^{14}$ g cm$^{-3}$. Applying the rates to magnetorotational supernovae jets and HMNS disk-wind trajectories, we find significant abundance-pattern changes in hot, moderately neutron-rich environments, accompanied by enhanced early heating that alters the final distribution. These results underscore the necessity of including finite-temperature $\beta$-decay in global $r$-process simulations and provide a practical rate grid to improve predictions for kilonova signatures.

Abstract

$β$-decay is known to play an essential role in the rapid neutron capture process ($r$-process) during $(n, γ) \leftrightarrow (γ, n)$ equilibrium and freeze-out when the neutron-rich nuclei decay back to stability. Recent systematic theoretical studies on $β$-decay at finite temperature indicated that under hot conditions ($T\sim10$~GK), a significant acceleration of $β$-decay rates is expected, especially for nuclei near stability. This corresponds to the early stage of the $r$-process. In this study, we investigate the effect of the $β$-decays in finite temperature using the rates calculated with the finite-temperature proton-neutron relativistic quasiparticle random-phase approximation (FT-PNRQRPA). We explore a variety of astrophysical conditions and find that the effect on the abundance pattern is significant in hot and moderately neutron-rich conditions such as are expected in magnetorotational supernovae. Accelerated $β$-decay rates also increase the heating rate in the early phase, resulting in an additional modification of the final abundance pattern.

Effect of Finite-Temperature $β$-Decay Rates on the Rapid Neutron Capture Process

TL;DR

Finite-temperature -decay rates can accelerate the -process flow during the hot early phase and influence freeze-out, with implications for the final abundance pattern and heating. We compute these rates using the FT-PNRQRPA framework, incorporating both allowed and first-forbidden transitions on grids up to GK and up to g cm. Applying the rates to magnetorotational supernovae jets and HMNS disk-wind trajectories, we find significant abundance-pattern changes in hot, moderately neutron-rich environments, accompanied by enhanced early heating that alters the final distribution. These results underscore the necessity of including finite-temperature -decay in global -process simulations and provide a practical rate grid to improve predictions for kilonova signatures.

Abstract

-decay is known to play an essential role in the rapid neutron capture process (-process) during equilibrium and freeze-out when the neutron-rich nuclei decay back to stability. Recent systematic theoretical studies on -decay at finite temperature indicated that under hot conditions (~GK), a significant acceleration of -decay rates is expected, especially for nuclei near stability. This corresponds to the early stage of the -process. In this study, we investigate the effect of the -decays in finite temperature using the rates calculated with the finite-temperature proton-neutron relativistic quasiparticle random-phase approximation (FT-PNRQRPA). We explore a variety of astrophysical conditions and find that the effect on the abundance pattern is significant in hot and moderately neutron-rich conditions such as are expected in magnetorotational supernovae. Accelerated -decay rates also increase the heating rate in the early phase, resulting in an additional modification of the final abundance pattern.

Paper Structure

This paper contains 5 sections, 1 figure.

Table of Contents

  1. Introduction
  2. Theoretical Method
  3. Finite-temperature beta-decay
  4. Nuclear physics inputs in nuclear reaction network calculation
  5. Astrophysical conditions

Figures (1)

  • Figure 1: (Upper panel) Temperature evolution of $\beta$-decay half-lives $T_{1/2}$ in tin isotopes ($Z = 50$) for a fixed $\rho Y_e = 10^8$ g/cm${}^3$. (Lower panel) The $\beta$-decay half-lives with respect to density $\rho Y_e$ for a fixed temperature $T = 2$ GK. The neutron numbers of particular tin isotopes are explicitly indicated.