Discovery of a PRS associated with FRB 20240114A

TL;DR

This paper reports the discovery of a fourth persistent radio source associated with a fast radio burst, using deep VLBA observations, and discusses its properties, location, and potential implications for FRB models.

Contribution

It provides the first deep VLBA detection of a PRS associated with FRB 20240114A, supporting the nebular model and characterizing its radio spectrum and host galaxy environment.

Findings

Detected a compact radio component 50 mas from the FRB position.

Radio luminosity and RM support the nebular model for the PRS.

Possible steepening of the radio spectrum in 1-5 GHz range.

Abstract

We present the discovery of the fourth persistent radio source (PRS) associated with a fast radio burst (FRB). Following previous indications of a candidate PRS associated with FRB20240114A, we performed deep VLBA observations at 5 GHz to test the presence of a compact radio source within the uncertainty position of this FRB ($\pm$200 mas). We detect a component $\sim$50 mas northwards the nominal position provided by the PRECISE collaboration. The corresponding radio luminosity, together with the Faraday rotation measure provided by previous observations of the FRB, locate this PRS in the expected region of the $L$ vs |RM| relation for the nebular model, further supporting it. The comparison of the measured flux density with the values collected at lower frequency by previous studies indicates a possible steepening of the radio spectrum in the 1-5 GHz range. Optical observations performed with the LBT could reveal that the FRB and its PRS lie at $\sim$1 kpc from the centre of the host galaxy, which is a dwarf sub-solar metallicity starburst galaxy with SFR $\sim 1 M_\odot\;\mathrm{yr^{-1}}$ and stellar mass $M\sim10^8 M_\odot$.