Detection of bursts from FRB 20250613A down to 300 MHz with uGMRT

ATel #17274; Yash Bhusare (NCRA -TIFR, India), Yogesh Maan (NCRA - TIFR), Ajay Kumar (NCRA - TIFR), Banshi Lal (NCRA - TIFR), Tarraneh Eftekhari (Northwestern University), and Shami Chatterjee (Cornell University)
on 6 Jul 2025; 09:10 UT
Credential Certification: Yogesh Maan (maan@astron.nl)

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Using the upgraded Giant Metrewave Radio Telescope (GMRT), we report the detection of 10 bursts from repeating fast radio burst FRB 20250613A that was recently discovered by the ASKAP team (Atel #17257). Observations were carried out from 2:30 to 5:30 UTC at Band 3 (300 - 500 MHz) on 2025 July 02 and at Band 4 (550 - 750 MHz) on 2025 July 03 (2:30 to 5:30 UTC). The on-source time was 86 minutes at Band 3 and 123 minutes at Band 4. Filterbank data were recorded from a phased-array beam and searched using the TransientX pipeline above a S/N threshold of 8 and at a single DM of 174.6 pc cm^-3 (as reported by the ASKAP team; Atel #17257). A more comprehensive search using coherently dedispersed and high time resolution data, over a range of DMs, is currently underway.

In Band 3 observations, we detected six bursts, with the emission in one of the bursts extending up to the lower edge of the band at 300 MHz. In Band 4 observations, we detected four bursts. Burst signal-to-noise (S/N) ratios range from 8 to 22 at Band 3 and from 11 to 44 at Band 4. Using the measured widths and S/N values from TransientX along with the radiometer equation, the burst fluences range from 0.5 to 2.5 Jy ms. The measured pulse-widths range between 1.5 ms and 22.3 ms. We also measured structure-optimised DMs of 174.72 +/- 0.09 and 174.75 +/- 0.12 pc cm^-3 for the brightest burst detected in Band 4 and Band 3, respectively, using DM_phase.

Detection of these new bursts shows that the emission from FRB 20250613A extends to frequencies as low as 300 MHz, and confirms continued activity of the source. We encourage further multi-frequency monitoring and especially observations at even lower radio frequencies.

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.

Dynamic spectra of a few bursts