The Sensitivity of Core-Collapse Supernovae to Nuclear Electron Capture

TL;DR

This study develops a library to assess how variations in nuclear electron-capture rates affect core-collapse supernovae, revealing significant sensitivities especially for neutron-rich nuclei near N=50, emphasizing the need for improved nuclear data.

Contribution

The paper introduces a systematic sensitivity analysis framework for electron-capture rates in supernova models, highlighting the impact of nuclear physics uncertainties on astrophysical outcomes.

Findings

Inner-core mass variation of +16/-4% at shock formation

Peak neutrino luminosity varies by ±20% during deleptonization

Greater sensitivity to rate reductions, especially for neutron-rich nuclei near N=50

Abstract

A weak-rate library aimed at investigating the sensitivity of astrophysical environments to variations of electron-capture rates on medium-heavy nuclei has been developed. With this library, the sensitivity of the core-collapse and early post-bounce phases of core-collapse supernovae to nuclear electron-capture is examined by systematically and statistically varying electron-capture rates of individual nuclei. The rates are adjusted by factors consistent with uncertainties indicated by comparing theoretical rates to those deduced from charge-exchange and $\beta$-decay measurements. To ensure a model independent assessment, sensitivity studies across a comprehensive set of progenitors and equations of state are performed. In our systematic study, we find a +16/-4 % range in the mass of the inner-core at the time of shock formation and a $\pm$20% range of peak {\nu}e-luminosity during the deleptonization burst. These ranges are each five times as large as those seen from a separate progenitor study in which we evaluated the sensitivity of these parameters to 32 presupernova stellar models. It is also found that the simulations are more sensitive to a reduction in the electron-capture rates than an enhancement, and in particular to the reduction in the rates for neutron-rich nuclei near the N = 50 closed neutron-shell. As measurements for medium-heavy (A > 65) and neutron-rich nuclei are sparse, and because accurate theoretical models which account for nuclear structure considerations on the individual nucleus level are not readily available, rates for these nuclei may be overestimated. If more accurate estimates confirm this, results from this study indicate that significant changes to the core-collapse trajectory can be expected. For this reason, experimental and theoretical efforts should focus in this region of the nuclear chart.