uGMRT detection of more than a hundred bursts from FRB 20220912A in 300 - 750 MHz frequency range

ATel #15806; Yash Bhusare (NCRA - TIFR, India), Ajay Kumar (NCRA - TIFR), Yogesh Maan (NCRA - TIFR), Visweshwar R. Marthi (NCRA - TIFR), Shriharsh Tendulkar (NCRA - TIFR), Banshi Lal (NCRA - TIFR), Hsiu-Hsien Lin (ASIAA/CITA), Robert Main (MPIfR, Germany), Arpan Pal (NCRA - TIFR)
on 13 Dec 2022; 05:52 UT
Credential Certification: Yogesh Maan (maan@astron.nl)

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We report the detection of more than a hundred bursts from FRB 20220912A in uGMRT Band 3 (300-500 MHz) and Band 4 (550-750 MHz) observations. The bursts show varying morphology and the emission distributed across different bursts cover the entire observed frequency range of 300 MHz to 750 MHz.

The source was observed on November 22 and 24, 2022, as a target of opportunity, following previous ATels (#15679, #15691, #15693, #15695, #15696, #15699, #15713, #15716, #15720, #15723, #15727, #15734, #15735) stating that FRB 20220912A was in a highly active state. On November 22, starting UTC 16:58:40 and 17:56:26, we conducted observations in the phased-array (PA) mode individually in Band 3 and Band 4 respectively, with around 30 minutes on-source time in each of the bands. On November 24, starting UTC 17:36:25, we observed the source simultaneously in Band 3 and Band 4 utilizing the dual-subarray PA mode for about a total of 1.3 hrs on-source time.

From our preliminary analysis, we have detected at least 32 bursts in Band 3 and 28 bursts in Band 4 above a signal-to-noise ratio detection threshold of 8, from our observations on November 22. The brightest detected bursts suggest that the fluence at the brighter end of the distribution is in excess of 5 Jy ms at Band 3 as well as Band 4. The bursts show a variety of morphologies, and temporal and spectral structures. Some of the bursts show emission at frequencies as low as 300 MHz. Some of the narrow bursts indicate the scatter broadening to be less than or around 15 ms at 400 MHz. A few examples of the bursts from each of the two bands can be found at: http://www.ncra.tifr.res.in/~ymaan/FRB20220912A_ATel.html .

In addition, from our simultaneous dual-band observations, we have detected 26 bursts in Band 3 and 45 bursts in Band 4 so far, out of which around 9 bursts appear to indicate emission that is detected in both the bands simultaneously.

Further analysis of these bursts as well as more refined search is underway. Given the current active state of FRB 20220912A, it will be useful to continue observing it in multiple bands.

We thank the staff of the GMRT for their support and assistance with these observations. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.

Example detection plots