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

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 8.88 × 10−7yr−1. The new glitches follow the seemingly unique time-to-next-glitch—glitch-size correlation established previously using RXTE data, with a slope of 5dμHz−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.

Diving below the Spin-down Limit: Constraints on Gravitational Waves from the Energetic Young Pulsar PSR J0537-6910

“…The sign change simply maintains consistency with the model from Jaranowski et al (1998). The cause of such gravitational-wave emission is a deviation from axial symmetry, which can be written in terms of a dimensionless equatorial ellipticity ε, defined in terms of the star's principal moments of inertia 1 and 2 and from Ho et al (2020b) and the latter from Antonopoulou et al (2018). Errors in n ig are 1σ uncertainty.…”

“…Its spin-down behavior appears to be driven by a process other than pure electromagnetic dipole radiation loss (at constant stellar magnetic field and moment of inertia). Specifically, its (long-term) braking indeẍ º =- n f f f 1.25 0.01 rot rot rot 2 , as measured over more than 20 yr (Ho et al 2020b), indicates an accelerating spin-down rate and significantly deviates from the measured values of most pulsars, n = 3, that imply dipole radiation (Shapiro & Teukolsky 1983).…”

“…In Ho et al (2020b), timing analysis is performed on NICER data of PSR J0537−6910 from 2017 August 17 to 2020 April 25, with eight glitches detected during this timespan and the last three glitches during O3. Here we present an update and results on timing analysis since the work of Ho et al (2020b). In particular, data from 2020 May 12 to October 29 are analyzed using the methodology as described in Ho et al (2020b).…”

“…Here we present an update and results on timing analysis since the work of Ho et al (2020b). In particular, data from 2020 May 12 to October 29 are analyzed using the methodology as described in Ho et al (2020b). Our analysis reveals continuing accelerated spin-down (see Table 1) and three subsequent glitches (see Table 2 and Figure 2), including the smallest glitch of PSR J0537−6910 yet detected using NICER.…”

“…Further observations with RXTE, prior to its decommissioning in early 2012, revealed that PSR J0537−6910 often undergoes sudden changes in rotation frequency, i.e., glitches, at a rate of more than three per year, and exhibits interesting interglitch behavior (Marshall et al 2004;Middleditch et al 2006;Andersson et al 2018;Antonopoulou et al 2018;Ferdman et al 2018). Observations of the pulsar resumed from 2017 to 2020 using the Neutron star Interior Composition Explorer (NICER) on board the International Space Station (Gendreau et al 2012), which revealed more glitches and a continuation of the timing behavior seen with RXTE (Ho et al 2020b).…”