A Persistently Active Fast Radio Burst source Embedded in an Expanding Supernova Remnant

TL;DR

This paper reports the discovery of a persistently active fast radio burst source embedded in an expanding supernova remnant, providing insights into its environment and long-term behavior over four years.

Contribution

It presents the first detailed long-term observation of a persistently active FRB and links its DM evolution to a dense, expanding supernova remnant environment.

Findings

FRB 20190520B is persistently active over four years.

The DM decreases at a rate of -12.4 pc cm^-3 yr^-1, much faster than in pulsars.

The source is likely embedded in a young supernova remnant.

Abstract

Fast radio bursts (FRBs) remain one of the most puzzling astrophysical phenomena. While most FRBs are detected only once or sporadically, we present the identification of FRB 20190520B as the first persistently active source over a continuous span of ~ four years. This rare long-term activity enabled a detailed investigation of its dispersion measure (DM) evolution. We also report that FRB 20190520B exhibits a substantial decrease in DM at a global rate of minus 12.4 plus or minus 0.3 pc cm^-3 yr^-1, exceeding previous FRB DM variation measurements by a factor of three and surpassing those observed in pulsars by orders of magnitude. The magnitude and consistency of the DM evolution, along with a high host DM contribution, strongly indicate that the source resides in a dense, expanding ionized medium, likely a young supernova remnant (SNR).