Synchrotron heating by a fast radio burst in a self-absorbed synchrotron nebula and its observational signature

TL;DR

This paper investigates how fast radio bursts (FRBs) can heat self-absorbed synchrotron nebulae, producing distinctive spectral features that could help identify embedded FRBs through their unique spectral hump.

Contribution

It introduces a model for synchrotron heating by FRBs in nebulae, predicting observable spectral signatures that can confirm the presence of an FRB within a nebula.

Findings

Nebula spectra develop a significant hump near the self-absorption frequency.

FRB photons are absorbed by nebula electrons, altering the electron energy distribution.

Spectral features can serve as observational signatures of embedded FRBs.

Abstract

Fast radio bursts (FRBs) are mysterious transient sources. If extragalactic, as suggested by their relative large dispersion measures, their brightness temperatures must be extremely high. Some FRB models (e.g. young pulsar model, magnetar giant flare model, or supra-massive neutron star collapse model) suggest that they may be associated with a synchrotron nebula. Here we study a synchrotron-heating process by an FRB in a self-absorbed synchrotron nebula. If the FRB frequency is below the synchrotron self-absorption frequency of the nebula, electrons in the nebula would absorb FRB photons, leading to a harder electron spectrum and enhanced self-absorbed synchrotron emission. In the meantime, the FRB flux is absorbed by the nebula electrons. We calculate the spectra of FRB-heated synchrotron nebulae, and show that the nebula spectra would show a significant hump in several decades near the self-absorption frequency. Identifying such a spectral feature would reveal an embedded FRB in a synchrotron nebula.