The Impact of a Supernova Remnant on Fast Radio Bursts

TL;DR

This paper investigates how young supernova remnants influence fast radio bursts, exploring observational signatures like dispersion measure and Faraday rotation, and constraining neutron star properties related to FRB origins.

Contribution

It presents a detailed analysis of the interaction between FRBs and SNRs, highlighting potential observational effects and constraints on neutron star magnetic fields and spin-down.

Findings

High DM associated with SNRs can be observed at 400 MHz to 1.4 GHz frequencies.

Free-free absorption can obscure FRBs for 100-500 years post-supernova.

Magnetic fields at the reverse shock may explain observed Faraday rotation in some FRBs.

Abstract

Fast radio bursts (FRBs) are millisecond bursts of radio radiation whose progenitors so far remain mysterious. Nevertheless, the timescales and energetics of the events have lead to many theories associating FRBs with young neutron stars. Motivated by this, I explore the interaction of FRBs with young supernova remnants (SNRs), and I discuss the potential observational consequences and constraints of such a scenario. As the SN ejecta plows into the interstellar medium (ISM), a reverse shock is generated that passes back through the material and ionizes it. This leads to a dispersion measure (DM) associated with the SNR as well as a time derivative for DM. Times when DM is high are generally overshadowed by free-free absorption, which, depending on the mass of the ejecta and the density of the ISM, may be probed at frequencies of $400\,{\rm MHz}$ to $1.4\,{\rm GHz}$ on timescales of $\sim100-500\,{\rm yrs}$ after the SN. Magnetic fields generated at the reverse shock may be high enough to explain Faraday rotation that has been measured for one FRB. If FRBs are powered by the spin energy of a young NS (rather than magnetic energy), the NS must have a magnetic field $\lesssim10^{11}-10^{12}\,{\rm G}$ to ensure that it does not spin down too quickly while the SNR is still optically thick at radio frequencies. In the future, once there are distance measurements to FRBs and their energetics are better understood, the spin of the NS can also be constrained.