Improved Nuclear Physics Near $A=61$ Refines Urca Neutrino Luminosities in Accreted Neutron Star Crusts

TL;DR

This study refines nuclear reaction rates and masses near A=61, leading to improved estimates of neutrino luminosities from urca cooling in accreted neutron star crusts, impacting models of X-ray bursts and cooling transients.

Contribution

It provides new nuclear mass measurements and reaction rates that enhance the modeling of urca neutrino emission in neutron star crusts.

Findings

Refined reaction rates for key isotopes near A=61.

Updated nuclear masses for $^{61}$V and $^{61}$Cr.

Improved estimates of urca neutrino luminosity in neutron star crusts.

Abstract

We performed a Penning trap mass measurement of $^{61}{\rm Zn}$ at the National Superconducting Cyclotron Laboratory and NuShellX calculations of the $^{61}{\rm Zn}$ and $^{62}{\rm Ga}$ structure using the GXPF1A Hamiltonian to obtain improved estimates of the $^{61}{\rm Zn}(p,\gamma)^{62}{\rm Ga}$ and $^{60}{\rm Cu}(p,\gamma)^{61}{\rm Zn}$ reaction rates. Surveying astrophysical conditions for type-I X-ray bursts with the code MESA, implementing our improved reaction rates, and taking into account updated nuclear masses for $^{61}{\rm V}$ and $^{61}{\rm Cr}$ from the recent literature, we refine the neutrino luminosity from the important mass number $A=61$ urca cooling source in accreted neutron star crusts. This improves our understanding of the thermal barrier between deep heating in the crust and the shallow depths where extra heat is needed to explain X-ray superbursts, as well as the expected signature of crust urca neutrino emission in light curves of cooling transients.