Neutron star mass-radius constraints using the high-frequency QPOs of GRB 200415A

TL;DR

This study uses observed high-frequency QPOs from a magnetar flare to constrain the neutron star's mass and radius by linking oscillation modes with nuclear matter properties and observational data.

Contribution

It introduces a method to infer neutron star properties by associating QPOs with crustal oscillations and nuclear saturation parameters, integrating observational and experimental constraints.

Findings

QPOs can be identified with crustal oscillation overtones.

Neutron star mass and radius are constrained by matching QPOs with nuclear parameters.

Constraints are consistent with other astronomical and experimental data.

Abstract

Quasi-periodic oscillations (QPOs) observed in a giant flare of a strongly magnetized neutron star (magnetar), are carrying crucial information for extracting the neutron star properties. The aim of the study is to constrain the mass and radius of the neutron star model for GRB 200415A, by identifying the observed QPOs with the crustal torsional oscillations together with the experimental constraints on the nuclear matter properties. The frequencies of the crustal torsional oscillations are determined by solving the eigenvalue problem with the Cowling approximation, assuming a magnetic field of about $10^{15}$G. We find that the observed QPOs can be identified with several overtones of crustal oscillations, for carefully selected combinations of the nuclear saturation parameters. Thus, we can inversely constrain the neutron star mass and radius for GRB 200415A by comparing them to the values of nuclear saturation parameters obtained from terrestrial experiments. We impose further constraints on the neutron star mass and radius while the candidate neutron star models are consistent with the constraints obtained from other available astronomical and experimental observations.