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

International audiencePSR 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 yr of NICER timing observations, from 2017 August to 2020 April. We obtain a rotation phase-connected timing model for the entire time span, 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 eight new glitches, the first detected since 2011, near the end of RXTE, with a total NICER and RXTE glitch activity of |$8.88\times 10^{-7}\, \mathrm{yr^{-1}}$|⁠. The new glitches follow the seemingly unique time-to-next-glitch–glitch-size correlation established previously using RXTE data, with a slope of |$5\, \rm {d} \, \mu \mathrm{Hz}^{-1}$|⁠. For one glitch around which NICER observes 2 d 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

Proper motion, spectra, and timing of PSR J1813–1749 using Chandra and NICER

International audiencePSR J1813–1749 is one of the most energetic rotation-powered pulsars known, producing a pulsar wind nebula (PWN) and gamma-ray and TeV emission, but whose spin period is only measurable in X-ray. We present analysis of two Chandra data sets that are separated by more than 10 yr and recent NICER data. The long baseline of the Chandra data allows us to derive a pulsar proper motion |$\mu _{\rm RA}=(-0.067\pm 0.010)\, \mathrm{ arcsec}\,\mathrm{yr^{-1}}$| and |$\mu _{\rm Dec.}=(-0.014\pm 0.007)\, \mathrm{ arcsec}\,\mathrm{yr^{-1}}$| and velocity |$v_\perp \approx 900\!-\!1600\, \mathrm{km\, s^{-1}}$| (assuming a distance d = 3–5 kpc), although we cannot exclude a contribution to the change in measured pulsar position due to a change in brightness structure of the PWN very near the pulsar. We model the PWN and pulsar spectra using an absorbed power law and obtain best-fitting absorption |$N_{\rm H}=(13.1\pm 0.9)\times 10^{22}\, \mathrm{cm^{-2}}$|⁠, photon index Γ = 1.5 ± 0.1, and 0.3–10 keV luminosity |L_{\rm X}\approx 5.4\times 10^{34}\, \mathrm{erg\, s^{-1}}(d/\mbox{ 5 kpc})^2| for the PWN and Γ = 1.2 ± 0.1 and |L_{\rm X}\approx 9.3\times 10^{33}\, \mathrm{erg\, s^{-1}}(d/\mbox{ 5 kpc})^2| for PSR J1813–1749. These values do not change between the 2006 and 2016 observations. We use NICER observations from 2019 to obtain a timing model of PSR J1813–1749, with spin frequency ν = 22.35 Hz and spin frequency time derivative |$\dot{\nu }=(-6.428\pm 0.003)\times 10^{-11}\, \mathrm{Hz\, s^{-1}}$|⁠. We also fit ν measurements from 2009 to 2012 and our 2019 value and find a long-term spin-down rate |$\dot{\nu }=(-6.3445\pm 0.0004)\times 10^{-11}\, \mathrm{Hz\, s^{-1}}$|⁠. We speculate that the difference in spin-down rates is due to glitch activity or emission mode switching