Internal superfluid response and torque evolution in the giant glitch of PSR J1718-3718

TL;DR

This paper models the post-glitch rotational behavior of pulsar PSR J1718-3718 using a vortex creep framework that includes inward and outward vortex motion and external torque changes, revealing insights into neutron star interior dynamics.

Contribution

It introduces a comprehensive vortex creep model with Bayesian parameter estimation to analyze pulsar glitches, linking internal superfluid dynamics to observable timing changes.

Findings

Inward vortex creep and external torque changes dominate the glitch evolution.

Estimated about 2.4 trillion inward-moving vortices involved.

Identified crustal plates of approximately 0.03 km in size.

Abstract

We investigate the post-glitch rotational evolution of pulsars by analyzing the 2007 giant glitch of PSR J1718$-$3718 using a vortex creep model that incorporates both inward and outward nonlinear vortex motion, along with a time-varying external torque. A comprehensive fitting framework is developed, constrained by prior knowledge of moment of inertia participation from previous glitch studies. We apply a Markov Chain Monte Carlo approach to quantify uncertainties and parameter correlations. The model reproduces the observed timing data and yields physically consistent values for moment of inertia fractions and creep timescales. Our results indicate that inward creep and a long-term change in external torque dominate the observed increase in spin-down rate, pointing to structural changes within the star-likely triggered by a crustquake that initiated both vortex motion and a change in the moment of inertia. We estimate that the glitch involved approximately $2.4 \times 10^{12}$ inward-moving vortices and $\sim 142$ crustal plates with a typical size of $\sim 0.03$ km. This study demonstrates that detailed post-glitch modeling of sparse timing data can simultaneously constrain internal superfluid dynamics and external torque evolution, providing a quantitative framework to probe the structural properties of neutron star interiors.