Neutron Star Dynamics under Time Dependent External Torques

TL;DR

This paper extends the two-component neutron star model to include arbitrary time-dependent external torques, enabling analysis of magnetars and binary neutron stars with variable spin behaviors.

Contribution

It provides solutions for neutron star dynamics under arbitrary external torques, including linear and nonlinear internal torque models, broadening applicability to diverse astrophysical objects.

Findings

Solutions for neutron star dynamics with time-dependent external torques.

Application to magnetars and binary neutron stars with variable timing.

Framework for using observed spin series to determine external torques.

Abstract

The two component model of neutron star dynamics describing the behaviour of the observed crust coupled to the superfluid interior has so far been applied to radio pulsars for which the external torques are constant on dynamical timescales. We recently solved this problem under arbitrary time dependent external torques. Our solutions pertain to internal torques that are linear in the rotation rates, as well as to the extremely non-linear internal torques of the vortex creep model. Two-component models with linear or nonlinear internal torques can now be applied to magnetars and to neutron stars in binary systems, with strong variability and timing noise. Time dependent external torques can be obtained from the observed spin-down (or spin-up) time series, $\dot{\Omega}(t)$.