Invariable X-Ray Profile and Flux of the Crab Pulsar during Its Two Glitches

Abstract

We compare the X-ray profiles and fluxes of the Crab pulsar before and after the glitches in 2017 and 2019, using the data collected by the Insight-HXMT, NICER, and Fermi/GBM, to test whether there is any evidence for magnetosphere rearrangement after glitch. For the 2017 glitch, the profiles from Insight-HXMT (27–200 keV) and NICER (0.5–10 keV) remain unchanged within rms 0.47% and 0.28%, respectively, while the pulsed fluxes measured by these two detectors remain stable with 1σ uncertainty of 0.07% and 0.011%. Considering that the persistent offset of the spin-down rate post-glitch is 0.13% and the X-ray luminosity of the Crab pulsar is proportional to E ̇ 1.6 ± 0.3 , we find that the X-ray flux does not increase proportionally to the spin-down power at a significance of about 2.8σ by fitting the flux measurements with a Heaviside function, and thus the additional torque constantly braking the pulsar spin post-glitch is unlikely due to a global magnetosphere variation. For the 2019 glitch, after which a possible soft X-ray polarization variation was detected, the profiles remain unchanged within rms 2.02%, 0.35%, 0.90%, and 0.47% in 10–200, 0.5–10, 3–4.5, and 27–200 keV, respectively, suggesting that the geometry of the X-ray emitting region after the glitch is similar to the pre-glitch one. Therefore the possible polarization variation during the 2019 glitch is unlikely a consequence of the overall magnetosphere changes. The invariance of the pulse profiles is also verified by Kolmogorov–Smirnov tests and that of pulsed fluxes by Z-tests.

A giant glitch from the magnetar SGR J1935+2154 before FRB 200428

“…Remarkably, in the evolution of the spin-down rate, a large persistent offset (∆ νp ) of −2.031 ± 0.019 pHz s −1 is present, which is 1.4 times of the spin-down rate ν before the glitch and is about one order of magnitude larger than the slow recovery component. Such a persistent offset should be due to an increase in the external torque caused by a rearrangement of the magnetosphere (Link et al 1992;Zhang et al 2022), and the large value implies that the magnetosphere changes dramatically at the glitch, consistent with the large pulse profile changes after G2 (Younes et al 2020) (Figure 3).…”

Spin Evolution of the Magnetar SGR J1935+2154

“…With FPCT analysis, the fitting parameters as listed in Table 2 show that G2 is frequency jump happened on MJD 58964.5(2.5) with Δν/ν = (6.4 ± 0.4) × 10 −2.031 ± 0.019 pHz s −1 is present, which is 1.4 times of the spin-down rate  n around MJD 58046-58130 and is about one order of magnitude larger than the slow recovery component. Such a persistent offset should be due to an increase in the external torque caused by a rearrangement of the magnetosphere (Link et al 1992;Zhang et al 2022), and the large value implies that the magnetosphere changes dramatically at the glitch, consistent with the large pulse profile changes after G2 (Younes et al 2020b) (Figure 3). The overall timing analyses have not given a very tight constraint on the occurrence time of G2.…”

Spin period evolution of Vela pulsar based on the wind emission: Application to the long period radio pulsars GPM J1839‐10 (P = 21 min) and GLEAM‐X J1627 (P = 18 min)

“…Over the past 55 years, more than 3,000 radio pulsars have been observed (Manchester et al 2005; Manchester and Taylor 1977), among which more than 800 radio pulsars have been observed by 500‐meter Aperture Spherical radio Telescope (FAST) (Han et al 2021; Li et al 2018; Wang et al 2021). Among them, the Crab and Vela pulsars are the young objects with supernova remnants (Malov 2021), which have been very well monitored and studied for a long time in various wavebands from radio to gamma rays (Lyne et al 1993), with the supernova remnants, pulsar wind nebula, and pulse glitches (Radhakrishnan and Manchester 1969; Zhang et al 2022b).…”