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MeerKAT discovery of a new repeating fast radio burst FRB 20240619D

ATel #16690; Jun Tian (University of Manchester), Ines Pastor-Marazuela (University of Manchester), Ben Stappers (University of Manchester), Kaustubh Rajwade (University of Oxford), Manisha Caleb (University of Sydney), MC (Tiaan) Bezuidenhout (North-West University), Fabian Jankowski (Universite d'Orleans), Ewan Barr (MPIfR), Michael Kramer (MPIfR), Rene Breton (University of Manchester), Mayuresh Surnis (IISER Bhopal), on behalf of the MeerTRAP team
on 5 Jul 2024; 09:30 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Jun Tian (jun.tian@manchester.ac.uk)

Subjects: Radio, Fast Radio Burst

Referred to by ATel #: 16732, 16745

The MeerTRAP team reports the discovery of a new repeating FRB source, FRB 20240619D. We detected three bursts within 2 minutes on 2024 June 19 with signal to noise ratios (S/Ns) of 28, 22 and 14, respectively. MeerKAT was operating in a sub-array mode at the time and 32 dishes were included in the sub-array which detected the FRB. All three bursts triggered channelised voltage data from the individual MeerKAT antennas, which we used to initially localise the FRB in the image domain using our transient buffer imaging pipeline (Rajwade et al. 2024; also see Rajwade et al. 2020). This FRB source is highly active given the limited exposure of MeerKAT at the source position (~2 minutes on 2024 June 19), as confirmed by further follow-up. A further investigation of archival MeerKAT observations of the field revealed two observations of similar duration in 2024 that did not reveal any bursts. The dynamic spectra of the three bursts are shown in the link below.

The three bursts occurred at 2024-06-19 00:41:01, 00:41:17, and 00:42:13 UTC (topocentric, at the top of the MeerKAT L-band which spans 856 - 1712 MHz). The S/N maximising DMs of the three bursts are 486.8, 480.7 and 471.9 pc cm^-3, respectively. A preliminary analysis of the voltage data shows that the brightest burst has a Faraday rotation measure of RM ~177 rad/m^2.

We carried out a 2h follow-up observation of FRB 20240619D with MeerKAT, 1h at L-band and 1h at S-band (1968 - 2843MHz), on 2024 June 26 at 00:09 UTC as part of a Director's Discretionary Time Proposal (proposal id: DDT-20240625-JT-01). The average burst rate observed at L-band and S-band is >70/h and >26/h, respectively, above a ~1 Jy ms fluence threshold. The best localisation was achieved using the voltage data of a bright burst detected at S-band at 2024-06-26 02:18:30 UTC, giving RA = 19:49:29.21, Dec = -25:12:49.40 with a 1-sigma uncertainty of 0.7 arcsec in RA and Dec. The localisation of the burst can be seen in the link below.

We find two optical sources in the images from the DESI Legacy Survey DR10 (Dey et al. 2019) near the FRB location, S1 at RA = 19:49:29.38, Dec = -25:12:48.80 and S2 at RA = 19:49:29.03, Dec = -25:12:47.77. No redshift information is available for these two sources. FRB 20240619D could potentially be associated with either of them or an even fainter galaxy. An extended radio source that we identify as AGN J194930.09-251338.6 from the Million Quasars catalogue is centred ~50 arcsec away from the FRB location. If this source is in the foreground of the FRB host, it could contribute to the observed DM and RM. Given that FRB 20240619D is likely still active now, we encourage further observations.

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.

Dynamic spectra and localisation of FRB 20240619D