Return of the Big Glitcher: NICER timing and glitches of PSR J0537-6910

TL;DR

This paper presents a detailed 2.7-year NICER timing analysis of the prolific glitching pulsar PSR J0537-6910, revealing new glitches, a long-term braking index of -1.25, and insights into glitch behavior and gravitational wave search potential.

Contribution

It provides the first long-term, phase-connected timing model for PSR J0537-6910, detects 8 new glitches, and analyzes glitch activity and braking index over an extended period.

Findings

Detected 8 new glitches since 2011.

Measured a long-term braking index of -1.25.

Confirmed the glitch size and time-to-next-glitch correlation.

Abstract

PSR J0537-6910, also known as the Big Glitcher, is the most prolific glitching pulsar known, and its spin-induced pulsations are only detectable in X-ray. We present results from analysis of 2.7 years of NICER timing observations, from 2017 August to 2020 April. We obtain a rotation phase-connected timing model for the entire timespan, which overlaps with the third observing run of LIGO/Virgo, thus enabling the most sensitive gravitational wave searches of this potentially strong gravitational wave-emitting pulsar. We find that the short-term braking index between glitches decreases towards a value of 7 or lower at longer times since the preceding glitch. By combining NICER and RXTE data, we measure a long-term braking index n=-1.25+/-0.01. Our analysis reveals 8 new glitches, the first detected since 2011, near the end of RXTE, with a total NICER and RXTE glitch activity of 8.88x10^-7 yr^-1. The new glitches follow the seemingly unique time-to-next-glitch---glitch-size correlation established previously using RXTE data, with a slope of 5 d microHz^-1. For one glitch around which NICER observes two days on either side, we search for but do not see clear evidence of spectral nor pulse profile changes that may be associated with the glitch.