FRB 190520B -- A FRB in a Supernova Remnant?

Abstract

FRB 190520B, a repeating FRB near-twin of FRB 121102, was discovered \citep{N21} to have a dispersion measure excess over the intergalactic and Galactic contributions of about 900 pc-cm$^{-3}$, attributable to its host galaxy or near-source environment. This excess varies on a time scale of $\sim 30\,$y and might be explained by a supernova remnant no more than a few decades old. A magnetic field in equipartition with the remnant's expansion would be ${\cal O}(1\,\text{G})$. I suggest the use of baseband data to measure very large rotation measures.