Investigating superconductivity in neutron star interiors with glitch models

TL;DR

This study examines how strong vortex pinning in neutron star cores affects pulsar glitch models, finding that observations suggest either type I superconductivity or weaker vortex-flux tube interactions.

Contribution

It applies realistic equations of state and relativistic models to analyze vortex pinning effects on pulsar glitches, providing new constraints on neutron star interior states.

Findings

Large core pinning is incompatible with Vela pulsar glitches.

Most of the core is likely in a type I superconducting state.

Vortex-flux tube interactions may be weaker than previously thought.

Abstract

The high density interior of a neutron star is expected to contain superconducting protons and superfluid neutrons. Theoretical estimates suggest that the protons will form a type II superconductor in which the stellar magnetic field is carried by flux tubes. The strong interaction between the flux tubes and the neutron rotational vortices could lead to strong 'pinning', i.e. vortex motion could be impeded. This has important implications especially for pulsar glitch models as it would lead to a large part of the vorticity of the star being decoupled from the 'normal' component, to which the electromagnetic emission is locked. In this paper we explore the consequences of strong pinning in the core on the 'snowplow' model for pulsar glitches (Pizzochero 2011), making use of realistic equations of state and relativistic background models for the neutron star. We find that in general a large fraction of pinned vorticity in the core is not compatible with observations of giant glitches in the Vela pulsar. The conclusion is thus that either most of the core is in a type I superconducting state or that the interaction between vortices and flux tubes is weaker than previously assumed.