Pulsar spin-down: the glitch-dominated rotation of PSR J0537-6910

TL;DR

This paper analyzes 13 years of timing data from pulsar PSR J0537-6910, revealing its unique glitch behavior, correlations, and long-term spin-down properties, providing new insights into neutron star physics.

Contribution

It presents the discovery of 22 new glitches, a comprehensive analysis of all 45 glitches, and insights into the glitch dynamics and spin-down behavior of PSR J0537-6910.

Findings

Strong correlation between glitch size and time to next glitch

Glitches occur at a rate of approximately 3.5 per year

The long-term braking index is negative, at -1.22

Abstract

The young, fast-spinning, X-ray pulsar J0537-6910 displays an extreme glitch activity, with large spin-ups interrupting its decelerating rotation every ~100 days. We present nearly 13 years of timing data from this pulsar, obtained with the {\it Rossi X-ray Timing Explorer}. We discovered 22 new glitches and performed a consistent analysis of all 45 glitches detected in the complete data span. Our results corroborate the previously reported strong correlation between glitch spin-up size and the time to the next glitch, a relation that has not been observed so far in any other pulsar. The spin evolution is dominated by the glitches, which occur at a rate ~3.5 per year, and the post-glitch recoveries, which prevail the entire inter-glitch intervals. This distinctive behaviour provides invaluable insights into the physics of glitches. The observations can be explained with a multi-component model which accounts for the dynamics of the neutron superfluid present in the crust and core of neutron stars. We place limits on the moment of inertia of the component responsible for the spin-up and, ignoring differential rotation, the velocity difference it can sustain with the crust. Contrary to its rapid decrease between glitches, the spin-down rate increased over the 13 years, and we find the long-term braking index $n_{\rm l}=-1.22(4)$, the only negative braking index seen in a young pulsar. We briefly discuss the plausible interpretations of this result, which is in stark contrast to the predictions of standard models of pulsar spin-down.