The Environment and Constraints on the Mass of FRB 190520B

TL;DR

This paper investigates the environment of FRB 190520B by analyzing its dispersion and rotation measure variations, constraining the size, electron density, magnetic field, and mass of the source region.

Contribution

It provides new constraints on the size, electron density, magnetic field, and mass of the dispersing region around FRB 190520B based on observational data.

Findings

Dispersion Measure fluctuates within fixed bounds, indicating a very compact dispersing region.

The magnetic field near the source is estimated to be around 500 microGauss.

Upper bounds on the dispersing region's size suggest a lower limit on the FRB source mass.

Abstract

Recent observations of FRB 20190520B have revealed rapid fluctuation of its Dispersion Measure within apparently fixed bounds, as well as a reversal of its Rotation Measure. The fluctuations of Dispersion Measure are uncorrelated with the intervals between bursts, setting upper bounds $\sim 10\,$s on any characteristic time scale of the dispersing region; it must be very compact. Measurements of the full dependence of the dispersive time delay on frequency may determine the actual electron density and the size of this region. It is possible to set a lower bound on the mass of the FRB source from constraints on the size of the dispersing region and its time scale of variation. Comparison of the variations of DM and RM leads to an estimate of the magnetic field $\sim 500\,\mu$G.