FRB 20121102A: images of the bursts and the varying radio counterpart

TL;DR

This study presents detailed radio imaging of FRB 20121102A, revealing a persistent radio source that decays over time and demonstrating MeerKAT's capability to localize FRBs with high sensitivity.

Contribution

First detailed radio images of FRB 20121102A's persistent source, showing flux decay and highlighting MeerKAT's potential for FRB localization through image plane detection.

Findings

Persistent radio source detected across multiple epochs

Flux density of the PRS decayed by over one-third in the final observation

MeerKAT can detect and localize FRBs with flux densities above 2.4mJy at 1.3GHz

Abstract

As more Fast Radio Bursts (FRBs) are being localised, we are learning that some fraction have persistent radio sources (PRSs). Such a discovery motivates an improvement in our understanding of the nature of those counterparts, the relation to the bursts themselves and why only some FRBs have PRSs. We report on observations made of FRB 20121102A with the MeerKAT radio telescope. Across five epochs, we detect the PRS associated with FRB 20121102A. Our observations are split into a cluster of four epochs (MJD 58732 - 58764) and a separate single epoch about 1000days later. The measured flux density is constant across the first four observations but then decays by more than one-third in the final observation. Our observations on MJD 58736 coincided with the detections of 11 bursts from FRB 20121102A by the MeerTRAP backend, seven of which we detected in the image plane. We discuss the importance of image plane detections when considering the commensal transient searches being performed with MeerKAT and other radio facilities. We find that MeerKAT is so sensitive that within a two-second image, we can detect any FRB with a flux density above 2.4mJy at 1.3GHz and so could localise every FRB that has been detected by CHIME to date.