Multifrequency constraints on the burst rate of FRB20220912A

ATel #16196; Graham Doskoch (West Virginia University), Susannah Paine (West Virginia University), Nathaniel Fairfield (amateur), Reshma Anna-Thomas (West Virginia University), Benetge Perera (Arecibo Observatory), Andrea Basurowski (North Carolina State University), Duncan Lorimer (West Virginia University), Maura McLaughlin (West Virginia University)
on 18 Aug 2023; 14:57 UT
Credential Certification: Maura McLaughlin (maura.mclaughlin@mail.wvu.edu)

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We report the detection of four bursts from FRB20220912A using the Green Bank 20-meter telescope. After its discovery by CHIME/FRB (ATel #15679), subsequent observations by a number of telescopes indicated the FRB exhibited an unusually high burst rate. We began two independent follow-up campaigns, one at L-band (1400 MHz) using the Green Bank 20m telescope and one at S-band (2300 MHz) using the Arecibo 12-meter telescope. Observation lengths range from 30 minutes to two hours. The L-band observations consisted of 91 hours of data taken between November 2, 2022 and January 4, 2023. The S-band observations consisted of ~120 hours of data taken between October 22, 2022 and April 8, 2023, with 1-hour daily observations. Both campaigns were supplemented by a 3-hour observation at 820 MHz using the 100-meter Green Bank Telescope (GBT) on January 4, 2023, during which all three telescopes observed the source simultaneously.

One burst was detected by the 12-m Arecibo telescope on October 27, 2022, and has already been reported (ATel#15734). We reduced the data using a simple Fast Dispersion Measure Transform (FDMT; Zackay & Ofek 2017) pipeline, along with a Heimdall-based pipeline, and detected four bright bursts in the 20m data set, at DM ~219 pc/cc, on November 18, November 19, and November 22, with topocentric times at infinite frequency and signal-to-noise ratio ratios (SNRs) given below.

Julian day (MJD)    SNR (Heimdall)
59901.74800074071 14.89
59902.81218165855 28.44
59905.74416028401 33.21
59905.89238238469 52.02

The January 4 observation featured all three telescopes observing simultaneously for three hours. We detected 25 bursts with the GBT, with the brightest having an SNR of ~270, while the 20m and 12m detected none. While this could be attributed to the large collecting area of the GBT, the extremely high SNRs of the brightest bursts suggest that other effects may be in play. The non-detections may be an indication that FRB20220912A possesses a steep spectrum. More work is underway to understand these bursts.

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