Magnetized neutron stars with superconducting cores: Effect of entrainment

TL;DR

This paper models magnetized neutron stars with superconducting cores, incorporating entrainment effects, revealing significant structural differences in magnetic field configurations compared to previous models.

Contribution

It introduces a numerical scheme for equilibrium models of neutron stars with entrainment effects in a Newtonian framework, advancing the understanding of magnetic field structures.

Findings

Entrainment causes qualitative changes in magnetic field line structure.

The improved numerical scheme enhances convergence in modeling.

Purely poloidal magnetic field configurations are analyzed.

Abstract

We construct equilibrium configurations of magnetized, two-fluid neutron stars using an iterative numerical method. Working in Newtonian framework we assume that the neutron star has two regions: the core, which is modelled as a two-component fluid consisting of type-II superconducting protons and superfluid neutrons, and the crust, a region composed of normal matter. Taking a new step towards more complete equilibrium models, we include the effect of entrainment, which implies that a magnetic force acts on neutrons, too. We consider purely poloidal field cases and present improvements to an earlier numerical scheme for solving equilibrium equations, by introducing new convergence criteria. We find that entrainment results in qualitative differences in the structure of field lines along the magnetic axis.