Magneto-rotational neutron star evolution: the role of core vortex pinning

TL;DR

This paper investigates how superfluid vortex pinning to magnetic fluxtubes in neutron star cores influences their rotational evolution, revealing differences between magnetars and radio pulsars and proposing a new magnetic field evolution timescale.

Contribution

It introduces a detailed analysis of core vortex pinning effects on neutron star spin-down and magnetic field evolution, highlighting implications for magnetar activity and magnetic field estimates.

Findings

Magnetars are likely in the vortex pinning regime.

Most radio pulsars are not affected by core pinning.

A new magnetic field evolution timescale is proposed.

Abstract

We consider the pinning of superfluid (neutron) vortices to magnetic fluxtubes associated with a type II (proton) superconductor in neutron star cores. We demonstrate that core pinning affects the spin-down of the system significantly, and discuss implications for regular radio pulsars and magnetars. We find that magnetars are likely to be in the pinning regime, while most radio pulsars are not. This suggests that the currently inferred magnetic field for magnetars may be overestimated. We also obtain a new timescale for the magnetic field evolution which could be associated with the observed activity in magnetars, provided that the field has a strong toroidal component.