Axisymmetric Cooling of Neutron Stars with Strong Magnetic Fields

TL;DR

This study uses full general relativity simulations to show that strong magnetic fields significantly alter neutron star cooling, affecting thermal relaxation times and the Direct Urca process, revealing magnetic influence on thermal evolution.

Contribution

It introduces a detailed 2D general relativistic model demonstrating how strong magnetic fields modify neutron star cooling and thermal relaxation.

Findings

Magnetic fields of 3-4×10^{17} G significantly affect cooling behavior.

Thermal relaxation time increases non-linearly with magnetic field strength.

Strong magnetic fields suppress the Direct Urca process in neutron stars.

Abstract

We study the cooling evolution of neutron stars with strong poloidal magnetic fields (with strength not far from observed values) using the full general relativity 2-dimensional \textit{Astreus} code, which solves consistently Einstein's and Maxwell's equations. We find that central magnetic fields with strengths $3-4\times10^{17}$ G, corresponding to surface magnetic fields $7-8\times10^{16}$, can significantly modify the cooling behavior of neutron stars, leading to stars with similar masses but different magnetic fields to exhibit different thermal evolution. We show a non-linear increase in the thermal relaxation time with increasing magnetic fields and that this behavior is associated with the reduction of the Direct Urca process in stars with strong magnetic fields. This is a novel result in which we can observe the magnetic field influence on the thermal evolution of stars, even if it is not strong enough to affect the Fermi distribution of particles.