Double-peaked Pulse Profile of FRB 200428: Synchrotron Maser Emission from Magnetized Shocks Encountering a Density Jump

TL;DR

This paper proposes a model where a density jump in the upstream medium causes the double-peaked pulse profile of FRB 200428, linking radio and X-ray emissions to magnetized shocks from a magnetar.

Contribution

It introduces a density jump scenario in magnetized shocks to explain the double-peaked structure and associated X-ray emission of FRB 200428, advancing magnetar-based FRB models.

Findings

Double-peaked FRB profile explained by density jump in shock environment.

Synchrotron emission from shock electrons accounts for X-ray fluence.

Model successfully reproduces observed luminosity and frequency of pulses.

Abstract

Very recently a fast radio burst (FRB) 200428 associated with a strong X-ray burst from the Galactic magnetar SGR 1935+2154 has been detected, which is direct evidence supporting the magnetar progenitor models of FRBs. Assuming the FRB radiation mechanism is synchrotron maser emission from magnetized shocks, we develop a specific scenario by introducing a density jump structure of upstream medium, and thus the double-peaked character of FRB 200428 is a natural outcome. The luminosity and emission frequency of two pulses can be well explained in this scenario. Furthermore, we find that the synchrotron emission of shock-accelerated electrons is in the X-ray band, which therefore can be responsible for at least a portion of observed X-ray fluence. With proper upgrade, this density jump scenario can be potentially applied to FRBs with multiple peaks in the future.