Non-detection of bursts from the repeating FRB 20251130A and upper limit on the associated PRS with uGMRT follow-up observations

ATel #17596; Ajay Kumar (NCRA - TIFR), Yash Bhusare (NCRA -TIFR, India), Yogesh Maan (NCRA - TIFR), Banshi Lal (NCRA - TIFR), Tarraneh Eftekhari (Northwestern University), and Shami Chatterjee (Cornell University)
on 14 Jan 2026; 18:43 UT
Credential Certification: Ajay Kumar (akumar@ncra.tifr.res.in)

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The MeerTRAP team recently reported the discovery of a new repeating fast radio burst (FRB) source, FRB 20251130A, with multiple bursts detected using MeerKAT and localized to arcsecond precision (ATel #17548). Given the precise localization, we conducted follow-up observations of FRB 20251130A with the upgraded Giant Metrewave Radio Telescope (uGMRT) in a phased-array mode.

We observed the source using the phased-array mode for a total of 144 minutes in band-3 (300-500 MHz), 130 minutes in band-4 (550-750 MHz) and 150 minutes in band-5 (1060-1460 MHz). The observations in band-4 started on 2025-12-19 23:30 and 2026-12-31 21:30, and in band-5 on 2025-12-22 21:30 UTC, with spectral and time resolutions of 48.82 kHz and 0.65536 ms, respectively. The observations in band-3 started on 2025-12-21 21:30 and 2026-01-01 23:30 UTC with spectral and time resolutions of 24.41 kHz and 0.65536 ms, respectively. No bursts were detected in our search over the DM range from 974 to 980 pc cm^-3. The typical 10 sigma fluence sensitivity limits of our observations are estimated to be 0.74 Jy ms, 0.63 Jy ms and 0.6 Jy ms in band-3, band-4 and band-5, respectively, assuming a 10 ms burst width.

One of our observations was conducted close in time to the observation in which a burst was detected with uGMRT at 650 MHz (ATel #17557), indicating that the source was active during this period. The non-detection of bursts in our observations despite the high sensitivity of uGMRT is consistent with either a sharp decline in burst activity following the discovery epoch or strong temporal clustering of bursts, also noted in ATel #17548. Such intermittency has been observed in several repeating FRB sources.

With our band-5 observations, we performed interferometric imaging using the CAPTURE pipeline (Kale et al. 2021). No source was detected at the location of the FRB. The 3 sigma upper limit on the flux density is 75 micro Jy/beam. Assuming the photometric redshift of the probable host galaxy reported in ATel #17548 (z = 0.41), this corresponds to an upper limit on the spectral luminosity of 3.4 × 10^29 erg/s/Hz. This derived upper limit is lower than the spectral luminosities of the PRSs associated with FRB 20121102A and FRB 20190520B, but higher than those of all other known FRB-PRS associations.

Continued multi-frequency monitoring will be essential to better constrain the burst rate, spectral behavior, and any activity cycles of FRB 20251130A.

We thank the observatory for prompt scheduling of our observations and the GMRT staff for their support. The GMRT is operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.

References: Kale, R., and Ishwara-Chandra, C. H. 2021, Experimental Astronomy, 51, 95, doi: 10.1007/s10686-020-09677-6