Magnetar QPOs and neutron star crust elasticity

TL;DR

This review explores how neutron star crust elasticity influences observed oscillations, using asteroseismology to connect magnetar flare signals with nuclear physics constraints.

Contribution

It systematically examines neutron star oscillations caused by crust elasticity and constrains nuclear saturation parameters through magnetar QPO analysis.

Findings

Identification of magnetar QPOs with torsional oscillations.

Constraints on nuclear saturation parameters from observed oscillations.

Dependence of shear and interface modes on neutron star properties.

Abstract

The crust region is a tiny fraction of neutron stars, but it has a variety of physical properties and plays an important role in astronomical observations. One of the properties characterizing the crust is the elasticity. In this review, with the approach of asteroseismology, we systematically examine neutron star oscillations excited by crust elasticity, adopting the Cowling approximation. In particular, by identifying the quasi-periodic oscillations observed in magnetar flares with the torsional oscillations, we make a constraint on the nuclear saturation parameters. In addition, we also discuss how the shear and interface modes depend on the neutron star properties. Once one detects an additional signal associated with neutron star oscillations, one can get a more severe constraint on the saturation parameters and/or neutron star properties, which must be a qualitatively different constraint obtained from terrestrial experiments, and help us to complementarily understand astrophysics and nuclear physics.