Detection of a PRS at 650 MHz associated with repeating FRB 20251229A using the uGMRT

ATel #17723; Ujjwal Panda (NCRA-TIFR), Jyotirmoy Das (NCRA-TIFR), Sanjay Kudale (NCRA-TIFR), Sridhar Gajendran (NCRA-TIFR), Chahat Dudeja (NCRA-TIFR), Kshitij Bane (NCRA-TIFR), and Jayanta Roy (NCRA-TIFR)
on 15 Mar 2026; 09:08 UT
Credential Certification: Ujjwal Panda (ujjwalpanda97@gmail.com)

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We report the detection of persistent radio emission (PRS) from the repeating FRB 20251229A. This source was first reported by the CHIME/FRB Collaboration in ATel #17574, with updated coordinates provided via baseband data in ATel #17606, and an outrigger-based localisation provided in ATel #17709. Subsequent detections were reported by HyperFlash/ECLAT in ATel #17588, FAST in ATel #17591, and the Northern Cross in ATel #17671. Considering its possible hyperactive nature, we proposed and carried out follow-up observations on this FRB on 8th February and 9th February, using uGMRT's Band 4 (550 to 750 MHz), and Band 3 (300 to 500 MHz) receivers, respectively. Using our Band 4 data with 2.87 hours of on-source time, we detected a compact radio source at RA (J2000) = 20h 41m 23.074s +/- 0.045s and Dec (J2000) = +16° 01' 26.760'' +/- 0.392'', with a peak flux of 64 +/- 13 uJy/beam, and a detection significance of 4.9 sigma. This much fainter detection at 550-750 MHz is consistent with the non-detection in VLASS (2-4 GHz), which has a 1-sigma RMS sensitivity of approximately 90 uJy/beam (ATel #17709). The source lies 12.64'' from the phase centre, and within the localisation uncertainty of both the CHIME baseband position given in ATel #17606, as well as the CHIME outrigger position given in ATel #17709. The detected source is spatially coincident with the optical galaxy SDSS J204123.23+160126.54 (as per SDSS DR16 catalog), or PSO J204123.232+160126.547 (as per PanSTARRS DR2 catalog), and has a photometric redshift of z = 0.12 as per the former, and z = 0.08 as per the latter. This detection of a persistent radio source supports the possibility that J204123.23+160126.54 is the most probable host galaxy of FRB 20251229A, as reported in ATel #17709. Assuming z = 0.08 as the redshift of the host galaxy, the estimated luminosity distance is ~375 Mpc, and the inferred spectral luminosity as per this luminosity distance is L_nu ~1.08 x 10^28 erg s^-1 Hz^-1. A plot of the radio image, overlaid on the optical image of the same field from PanSTARRS, can be found at the link below. We would like to thank the approving authority of the Director's Discretionary Time and the observatory operations group for the prompt allocation and scheduling of our observations, as well as the GMRT staff that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.

Plot showing our detection from the GMRT, overlaid on the corresponding PanSTARRS field.