Confirmation of a compact persistent radio source associated with FRB20240114A

ATel #16885; Gabriele Bruni (INAF-IAPS), Luigi Piro (INAF-IAPS), Luciano Nicastro (INAF-OAS), Eliana Palazzi (INAF-OAS), Yuan-Pei Yang (Yunnan University), Bing Zhang (University of Nevada)
on 30 Oct 2024; 09:40 UT
Credential Certification: Gabriele Bruni (gabriele.bruni@inaf.it)

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We performed VLBA observations of the candidate PRS associated with FRB20240114A. The source was previously detected with uGMRT and MeerKAT at lower angular resolution (a few arcsec, ATel #16820 and Atel #16695), not allowing to exclude a possible star-formation or diffuse origin. Lately, further e-Merlin observations at 5.5 GHz performed by us resulted in a 50 uJy upper limit (ATel #16864), suggesting a steep spectral index (<-0.6) in the 1.3-5 GHz range, or that the radio emission comes from a diffuse region (>~460 mas corresponding to a physical size >~1 kpc) resolved-out at the resolution of e-Merlin (tens of milli-arcsec).

We observed with the VLBA at 5 GHz (C band), under DDT project BB468 (PI Bruni), pointing at the FRB coordinates from the PRECISE collaboration (ATel #16542). Observations were divided into two runs, on September 28th and 30th, 2024, for a total of 12 hours. Phase referencing was applied. Data were reduced through the standard AIPS procedure for continuum, then calibrated visibilities from the two runs were concatenated and imaged in CASA achieving an angular resolution of 4x2 milli-arcsec in natural weighting.

An unresolved source was identified within the +/-200 mas FRB positional uncertainty provided by the PRECISE collaboration, ~50 mas northwards the phase center. The flux density is ~40 uJy, thus falling below the e-Merlin upper limit at the same frequency from our previous observations (ATel #16864). No other statistically significant peak was found in the uncertainty region from PRECISE. At the redshift of the host galaxy (z=0.13, ATel #16613), the physical size of the PRS is constrained to <~5 pc.

This detection confirms the presence of a compact, continuum source associated with FRB20240114A, making this the fourth PRS known to date - following FRB20121102A (Marcote et al. 2017), FRB20190520B (Bhandari et al. 2023a), and FRB20201124A (Bruni et al. 2024). Results will be discussed in a forthcoming paper (Bruni et al. in prep.).

References: Marcote et al. 2017 ApJL, 834, L8; Bhandari et al. 2023a, ApJL, 958, L19; Bruni et al. 2024, Nature, 632, 8027;

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Programme and operated under licence.