Spectrum of shear modes in the neutron-star crust: Estimating the nuclear-physics uncertainties

TL;DR

This paper models neutron-star crust shear modes using chiral EFT interactions, analyzing uncertainties in nuclear physics inputs and their effects on observable oscillation frequencies.

Contribution

It systematically evaluates nuclear physics uncertainties on crustal shear properties and mode spectra, linking theoretical models to astrophysical observations.

Findings

Uncertainties mainly stem from neutron-matter EOS and neutron entrainment.

Crustal shear mode frequencies are consistent with observed QPOs within current uncertainties.

Current uncertainties prevent precise inference of neutron-star properties from observations.

Abstract

I construct a model of the inner crust of neutron stars using interactions from chiral effective field theory (EFT) in order to calculate its equation of state (EOS), shear properties, and the spectrum of crustal shear modes. I systematically study uncertainties associated with the nuclear physics input, the crust composition, and neutron entrainment, and estimate their impact on crustal shear properties and the shear-mode spectrum. I find that the uncertainties originate mainly in two sources: The neutron-matter EOS and neutron entrainment. I compare the spectrum of crustal shear modes to observed frequencies of quasi-periodic oscillations in the afterglow of giant $\gamma$-ray bursts and find that all of these frequencies could be described within uncertainties, which are, however, at present too sizable to infer neutron-star properties from observations.