Rotational Coupling of the Pinned Core Superfluid

TL;DR

This paper investigates how pinning between fluxoids and vortices in a neutron star's core affects the superfluid's rotational dynamics, revealing that pinning significantly influences core-crust coupling and post-glitch behavior.

Contribution

It introduces a detailed calculation of the core superfluid's coupling timescale considering finite frictional pinning forces, highlighting its dominance over electron scattering in most scenarios.

Findings

Pinning impedes vortex motion but does not block it entirely.

The coupling timescale is primarily determined by pinning-related friction.

Different post-glitch responses depend on vortex behavior and pinning effects.

Abstract

The effects of pinning between fluxoids and vortices in the core of a neutron star, on the dynamics of the core neutron superfluid are considered. The pinning impedes, but does not absolutely block, any radial as well as {\em azimuthal} motion of the neutron vortices with respect to the lattice of fluxoids. The time scale for the coupling of rotation of the core superfluid to the rest of the star is calculated, allowing for the effect of the finite frictional force on the neutron vortices due to their pinning with the fluxoids. This turns out to be the dominant mechanism for the coupling of the core of a neutron star to its crust, as compared to the role of electron scattering, for most cases of interest. Furthermore, different behaviors for the post-glitch response of the core superfluid are distinguished that might be tested against the relevant observational data. Also, a conceptually important case (and controversial too, in the earlier studies on the role of the crustal superfluid) is realized where a superfluid may remain decoupled in spite of an spinning up of its vortices.