Detection and localisation of the highly active FRB 20240114A by MeerKAT

ATel #16446; Jun Tian (University of Manchester), Ines Pastor-Marazuela (University of Manchester), Ben Stappers (University of Manchester), Kaustubh Rajwade (ASTRON), Manisha Caleb (University of Sydney), MC (Tiaan) Bezuidenhout (North-West University), Ewan Barr (MPIfR), Michael Kramer (MPIfR), on behalf of the MeerTRAP team
on 14 Feb 2024; 12:24 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Jun Tian (jun.tian@manchester.ac.uk)

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We report the localisation of the repeating FRB 20240114A using two bursts detected with MeerKAT. We carried out a 1h L-band observation of FRB 20240114A on 9 February 2024 at 08:41 UT in the frequency range between 856-1712 MHz as part of a Director's Discretionary Time Proposal (proposal id: DDT-20240206-JT-01), following reports of its possible hyper-activity by the CHIME/FRB (ATel #16420), Parkes (ATel #16430) and FAST (ATel #16433) telescopes.

When triggered, MeerTRAP can capture channelised voltage data from the individual MeerKAT antennas, which can be used for localisation in the image domain using our transient buffer imaging pipeline (Rajwade et al. in prep; also see Rajwade et al. 2020, Society of Photo-Optical Instrumentation Engineers Conference Series Vol. 11447, Ground-based and Airborne Instrumentation for Astronomy VIII. p. 114470J). We used the transient buffer data from the two brightest bursts, detected S/N of 19.47 and 49.22 respectively, to localise FRB 20240114A. The S/N maximising DM of these two bursts is 529.31 pc cm^-3 and 531.26 pc cm^-3.

The two bursts were localised to the following best-fit positions (epoch J2000):
RA: 21:27:39.83
Dec: +04:19:46.02
MJD (topocentric, at the top of the MeerKAT L-band): 60349.36998543
and
RA: 21:27:39.84
Dec: +04:19:46.34
MJD (topocentric, at the top of the MeerKAT L-band): 60349.37061473

The total uncertainty in the burst position is composed of two components, a statistical component from source fitting in the FRB image and a systematic component from the astrometric correction. We used the Rapid ASKAP Continuum Survey (RACS) catalogue (McConnell et al. 2020, PASA, 37, e048) as the reference frame to correct the astrometry in the MeerKAT images. The total uncertainty is currently ~1.5 arcsec with the astrometric uncertainty being dominant. Improvements may be possible with more bursts and deeper images of the field. The localisation of the FRB 20240114A source can be seen in the link below.

The two bursts are spatially coincident with J212739.84+041945.8, a galaxy cataloged in the Sloan Digital Sky Survey with a photometric redshift of z = 0.42 (Alam et al. 2015, ApJS, 219, 12). Using the Probabilistic Association of Transients to their Hosts (PATH, Aggarwal et al. 2021, ApJ, 911, 95) software, we found the association probability with this galaxy to be 0.9974, assuming the prior on an unseen host of 0.2. This redshift, if confirmed, lies in the range of the highest redshift cluster of galaxies identified in ATel #16426. FRB 20240114A is still active and we encourage continued radio observations of the source and multi-wavelength follow-up of its host galaxy.

We would like to thank the Director and the operators of MeerKAT and the South African Radio Astronomy Observatory (SARAO) for the prompt scheduling of the observation. The MeerKAT telescope is operated by SARAO, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation.

Localisation of FRB 20240114A overlaid on the DESI-Legacy Survey DR10 optical image