Understanding FRB 200428 in the Synchrotron Maser Shock Model: Consistency and Possible Challenge

Abstract

Recently, the discovery of Galactic FRB 200428 associated with an X-ray burst (XRB) of SGR 1935+2154 has built a bridge between FRBs and magnetar activities. In this Letter, we assume that the XRB occurs in the magnetar magnetosphere. We show that the observational properties of FRB 200428 and the associated XRB are consistent with the predictions of synchrotron maser emission at ultrarelativistic magnetized shocks, including radiation efficiency, similar energy occurrence frequency distributions, and simultaneous arrive times. It requires that the upstream medium is a mildly relativistic baryonic shell ejected by a previous flare. The energy injection by flares responsible for the radio bursts will produce a magnetar wind nebula, which has been used to explain the persistent radio source associated with FRB 121102. We find that the radio continuum around SGR 1935+2154 can be well understood in the magnetar wind nebula model, by assuming the same energy injection rate as FRB 121102. The required baryonic mass is also estimated form the observations of FRB 121102 by the Green Bank Telescope and the Five-hundred-meter Aperture Spherical Telescope. By assuming the same radiation efficiency , the total baryonic mass ejected from the central magnetar is about 0.005 solar mass. This value is much larger than the typical mass of a magnetar outer crust, but is comparable to the total mass of a magnetar crust.

The physics of fast radio bursts

“…Its duration is of order ∼ milliseconds, and the luminosity and spectrum highly depends on the flare parameters. This model has been successfully applied to FRB 200428 in different details [215,216,223,224]. The observed low efficiency E radio /E X ∼ 10 −5 of FRB 200428 matches the model prediction well.…”

Dispersion and Rotation Measures from the Ejecta of Compact Binary Mergers: Clue to the Progenitors of Fast Radio Bursts

“…For t age ∼ 10 yr and δ 1, the RM WN is ∼ 10 5 rad m −2 . The time-dependent radio luminosity and the RM WN of FRBs with different ages can be well explained in this model (Wu et al 2020). The DM due to the nebula (Hilmarsson et al 2020) is…”

“…Obviously, the merger rate of BNS or NSWD is lower than FRBs (E < 10 31 erg Hz −1 ). Based on the gravitational-wave events observed by the Advanced LIGO/Virgo gravitationalwave detectors, Zhang et al (2020) also found that only a small fraction of repeating FRBs are produced by young magnetars from BNS mergers. From the local event rate of compact binary mergers, the value of ρ BWD (0) is close to ρ FRB (0).…”

Fast Radio Bursts

“…Another simulation showed that low-amplitude Alfvén waves from a magnetar quake can be convert to plasmoids, afterwards, collision with the wind will lead to blast waves [184]. However, this mechanism also have some defects as being disfavored recently by observations, such as the baryonic mass budget [169], the PA swing [90] and nano-second variability [112].…”