Spin Evolution of the Magnetar SGR J1935+2154

Abstract

Fast radio bursts (FRBs) are short pulses observed in radio frequencies usually originating from cosmological distances. The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154 suggests that at least some FRBs can be generated by magnetars. However, the majority of X-ray bursts from magnetars are not associated with radio emission. The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs. Here we report long time spin evolution of SGR J1935+2154 until the end of 2022. According to $\nu$ and $\dot\nu$, the spin evolution of SGR J1935+2154 could be divided into two stages. The first stage evolves relatively steady evolution until April 27, 2020. After the burst activity in 2020, the spin of SGR J1935+2154 shows strong variations, especially for $\dot\nu$. After the burst activity in October 2022, a new spin-down glitch with $\Delta\nu/\nu=(-7.2\pm0.6)\times10^{-6}$ is detected around MJD 59876, which is the second event in SGR J1935+2154. At the end, spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021, which supply strong clues to constrain the trigger mechanism of FRB or radio bursts.

The Physical Origin of the Periodic Activity for FRB 20180916B

“…Such kind of a glitches have been discovered in accretion-powered pulsars by Serim et al (2017) and Galloway et al (2004) with a sudden frequency change of Δv = 1.28(5) × 10 −6 Hz and Δv = 1.8 × 10 −6 Hz. These glitches are similar to the giant glitches of SGR J1935+2154 occurring before FRB-like bursts (Ge et al 2024;Hu et al 2024). Such glitches could alter the core magnetic field during the relaxation phase of the glitch, which will eventually trigger the movement of the crust and produce FRBs through the crust quakes (Wang et al 2018;Suvorov & Kokkotas 2019).…”

Temporal and Spectral Characteristics of Persistent Emission and Special Bursts of Magnetar SGR J1935+2154 Based on Insight-HXMT

“…For the persistent emission analysis, we employ the Insight-HXMT LE data which excluded any potential burst signals, and also the solar system barycenter correction was carried out before phase analysis. The ephemeris derived from NICER data with f = 0.3075277 Hz and f1 = −3.92 × 10 −12 Hz s −1 (at T 0 = 59865 MJD) in Ge et al (2024) were used to find the most significant LE data segment which can be used for phase analysis. Finally, the observation data segments 59871.0876 MJD to 59880.4756 MJD and 59882.33867 MJD to 59884.20446 MJD were found to exhibit significant persistent radiation signals within the energy range of 0.74-5.85 keV.…”

“…Due to the large margin of errors, here we just give a simple result of Insight-HXMT pulse period search. When we do burst phase analysis, the ephemeris data f = 0.3075277 Hz and f1 = −3.92 × 10 −12 Hz s −1 (at T 0 = 59865 MJD) in Ge et al (2024) were selected for a long time span.…”

“…No more detailed results have been reported. In Ge et al (2024) the spin properties based NICER has been reported with f = 0.3075277 Hz and f1 = −3.92 × 10 −12 Hz s −1 at T 0 = 59865 MJD. The spin evolution of SGR J1935+2154 is found to be steady around the time of the radio bursts 221 014 and 221 021.…”

Insights from the Gaussian Process Method for the Fast Radio Burst–associated X-Ray Burst of SGR 1935+2154

“…The glitch involved changes in the frequency (Δν = 19.8 ± 1.4 μHz) and spin-down rate ( n D =  6.3  1.1 pHz s −1 ). The associated change in the spin-down power rate, n n D  , ranks among the highest observed in pulsar glitches, including a delayed spin-up process (Ge et al 2024). There are indications of temporal spectral hardening linked to the occurrence of two peaks in the XRB (Mereghetti et al 2020;Li et al 2021).…”