The anisotropy and magnetic field structure of neutron stars through gravitational wave

TL;DR

This paper explores how gravitational wave observations can reveal the internal anisotropic and magnetic field structures of neutron stars by modeling their effects on mass, deformability, and GW signals.

Contribution

It extends the TOV framework to include pressure anisotropy and magnetic fields, analyzing their impact on neutron star properties and GW signatures.

Findings

Anisotropy and magnetic fields increase maximum neutron star mass.

Magnetic field configurations affect tidal deformability and GW signals.

Discrimination of internal structures possible at SNRs around 18.

Abstract

We investigate how gravitational wave (GW) observations can probe the internal physics of neutron stars by extending the Tolman-Oppenheimer-Volkoff framework to include pressure anisotropy and internal magnetic fields. Two representative magnetic field configurations, radial orientation dominated (RO) and transverse orientation dominated (TO), are implemented with strength and decay prescriptions. We found that both anisotropy and magnetic fields increase the maximum supported mass and modify the tidal deformability $\Lambda$, thereby imprinting measurable signatures on GW signals. For the equal mass binary ($1.2M_\odot$-$1.2M_\odot$), anisotropy neutron star with RO magnetic field yield more compact stars and a larger shift in $\Lambda$, allowing discrimination at signal-to-noise ratios (SNRs) as low as $\sim18$ using the O4 power spectra density. TO fields produce weaker effects and require substantially higher SNRs for detection. In conclusion, we conclude that gravitational waves are capable of probing the internal structure of neutron stars.