FRB 20200428 and potentially associated hard X-ray bursts: Maser emission and synchrotron radiation of electrons in a weakly magnetized plasma?

TL;DR

This paper models the association between FRB 20200428 and X-ray bursts from SGR 1935+2154 using plasma maser emission and synchrotron radiation in weakly magnetized, relativistic plasma blobs, predicting observable signals and constraining blob properties.

Contribution

It introduces a novel model linking FRB and X-ray bursts through plasma maser and synchrotron emission, with detailed parameter constraints and simulation predictions.

Findings

Model predicts observable FRB and X-ray bursts with current telescopes.

Blob properties are constrained: Lorentz factor 5-30, magnetization factor 6e-5 to 2e-4.

Flux density variation can explain sub-energetic and giant radio pulses.

Abstract

The temporal and spatial coincidence between FRB 20200428 and hard peaks of the X-ray burst from SGR 1935+2154 suggests their potential association. We attributed them to the plasma synchrotron maser emission and synchrotron radiation of electrons in weakly magnetized, relativistically moving plasma blobs, and Monte Carlo simulation analysis shows that our model can predict observable fast radio burst outbursts and associated hard X-ray bursts with current telescopes. We constrained the properties of the blobs, including the Lorentz factor $\Gamma=5-30$, the magnetization factor $\sigma=6\times10^{-5}\sim 2\times 10^{-4}$, the electron Lorentz factor $\gamma_{\rm e,s}=(1.8-3.3)\times10^4$, and the plasma frequency $\nu_P=2.48 -42.61$ MHz. The inferred size of the blobs is $\sim 10^{9-10}$ cm, and it is located $\sim 10^{12-14}$ cm from the central engine. By adopting fine-tuned parameter sets, the observed spectra of both the FRB 20200428 outbursts and X-ray bursts can be well represented. The peak flux density ($F_{\rm\nu_{ pk}}$) of plasma maser emission is sensitive to $\sigma$ and $\nu_P$. Variation in $F_{\rm \nu_{pk}}$ can be more than 10 orders of magnitude, while the flux density of the synchrotron emission only varies by $1-2$ orders of magnitude. This can account for the observed sub-energetic radio bursts or giant radio pulses from SGR 1935+2154.