Constraining the Supernova Remnant Environment of FRB 190520B with Dispersion Measure and Scattering Timescale

FRB 190520B is a repeating fast radio burst source whose large dispersion measure (DM) and temporal broadening suggest a dense and evolving local environment. In this work, we test the possibility that FRB 190520B originates from the core-collapse of a massive star so that its central engine is embedded in a supernova remnant (SNR) expanding into a wind environment, whose evolution is described by the self-similar solution. We use the observed DM and scattering timescale of FRB 190520B to constrain the physical parameters of its surrounding SNR and host-galaxy DM. Twenty typical cases are considered, arising from four ejecta profiles and five scattering prescriptions. It is found that only 6 cases are retained and provide acceptable fits. All retained cases have a shallow ejecta profile and a young source age of $t_0=79.8$--$169.8~{\rm yr}$. The ejecta mass is inferred to be large for all six cases, while the kinetic energy and mass-loss rate span a wide range. The secular DM evolution is reproduced better than the detailed scattering evolution. The up-drift behavior of the scattering residual suggests an additional component or more complicated structures inside the SNR. All retained cases are self-consistent within the adopted scattering theory and the circum-burst medium becomes transparent for GHz bursts before the inferred source ages.