Global numerical simulations of the rise of vortex-mediated pulsar glitches in full general relativity

TL;DR

This study uses full general relativity simulations to analyze pulsar glitches, revealing that relativistic effects significantly influence glitch dynamics and gravitational wave emissions, with implications for observational detection.

Contribution

First detailed numerical simulations of pulsar glitches in full general relativity, highlighting the impact of relativistic effects on glitch rise times and gravitational wave signals.

Findings

Relativistic effects can alter glitch rise times by up to 40%.

Exponential law accurately describes angular velocity evolution.

Gravitational wave signals from glitches are potentially detectable.

Abstract

In this paper, we study in detail the role of general relativity on the global dynamics of giant pulsar glitches as exemplified by Vela. For this purpose, we carry out numerical simulations of the spin up triggered by the sudden unpinning of superfluid vortices. In particular, we compute the exchange of angular momentum between the core neutron superfluid and the rest of the star within a two-fluid model including both (non-dissipative) entrainment effects and (dissipative) mutual friction forces. Our simulations are based on a quasi-stationary approach using realistic equations of state (EoSs). We show that the evolution of the angular velocities of both fluids can be accurately described by an exponential law. The associated characteristic rise time $\tau_{\text{r}}$, which can be precisely computed from stationary configurations only, has a form similar to that obtained in the Newtonian limit. However, general relativity changes the structure of the star and leads to additional couplings between the fluids due to frame-dragging effects. As a consequence, general relativity can have a large impact on the actual value of $\tau_{\text{r}}$: the errors incurred by using Newtonian gravity are thus found to be as large as $\sim 40 \%$ for the models considered. Values of the rise time are calculated for Vela and compared with current observational limits. Finally, we study the amount of gravitational waves emitted during a glitch. Simple expressions are obtained for the corresponding characteristic amplitudes and frequencies. The detectability of glitches through gravitational wave observatories is briefly discussed.