Stationary, Axisymmetric Neutron Stars with Meridional Circulation in General Relativity

TL;DR

This paper introduces a novel model for stationary, axisymmetric neutron stars with meridional circulation in general relativity, revealing how vortices influence surface deformation and expanding understanding of neutron star fluid dynamics.

Contribution

The authors developed GRNS, a new computational code, to model neutron stars with meridional circulation, providing the first such models in general relativity.

Findings

Meridional circulation modes form a two-dimensional set with varying vortex counts.

Surface deformations of about 1% occur at circulation velocities around 1000 km/s.

Models show that vortices near the surface significantly affect star shape and deformation.

Abstract

We present the first stationary, axisymmetric neutron star models with meridional circulation in general relativity. For that purpose, we developed GRNS, a new code based on a fixed point iteration. We find a two-dimensional set of meridional circulation modes, which differ by the number of vortices in the stream lines of the neutron star fluid. For expected maximal meridional circulation velocities of about 1000 km/s, the vortices cause surface deformations of about a percent. The deformations depend on the shape of the vortices close to the surface and increase with the meridional circulation velocity. We also computed models of rotating neutron stars with meridional circulation, where neither the surface rotates nor does the rotation velocity exceed the circulation velocity.