Non-detection of radio pulses from GRB 210119A/Swift J1851.2-6148 with Parkes

ATel #14347; Marcus E. Lower (Swinburne University of Technology, SUT), Rahul Sengar (SUT), Pravir Kumar (SUT) and Ryan M. Shannon (SUT)
on 26 Jan 2021; 02:52 UT
Credential Certification: Marcus Lower (mlower@swin.edu.au)

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Following the Swift-BAT detection of a short burst from either a gamma-ray burst (GRB) or undiscovered soft gamma-ray repeater (SGR) in the Galactic bulge (GCN #29323), we conducted a target of opportunity observation of the source with the Parkes radio telescope using the Ultra-Wideband Low receiver system (Hobbs et al. 2020), starting at UTC 2021-01-19-22:13:21.

We recorded 2777 seconds of pulsar search-mode data using both the DFB4 (3.1 GHz central frequency, 1024 MHz bandwidth, 256 microsec time resolution) and Medusa (2.368 GHz central frequency, 3328 MHz bandwidth, 64 microsec time resolution) backend recording systems. After flagging channels affected by radio-frequency interference, we searched the DFB4 data for periodic signals using both the peasoup (Barr 2020) and PRESTO (Ransom 2001) pulsar-search packages with dispersion measure (DM) trials ranging between 0-1000 pc/cm^3 and a S/N threshold of 7. Visual inspection of the output candidates did not identify any positive pulsar candidates. Additionally, no candidates were found in a separate search of the Medusa data split into two subbands covering 1230-1790 MHz and 1030-2030 MHz using the peasoup package.

Both the DFB4 and Medusa data were searched for single pulses and fast radio bursts (FRBs) using Heimdall (Barsdell 2012) and Fetch (Agarwal et al. 2020) over a DM range of 50-1000 pc/cm^3. Data were searched using a tiered sub-band strategy as described in Kumar et al. (2021). No significant candidates were identified.

The lack of any associated radio pulses is consistent with the gamma-ray burst originating from either a radio-quiet Galactic SGR or an extragalactic short GRB. However, we note that subsequent spectral analysis of the Swift-BAT data (GCN #29332) and the detection of the burst by GECAM-B (GCN #29331) both suggest a short GRB origin is most probable. If a millisecond magnetar was born during the GRB, then we can rule out the emission of 1 ms width FRBs down to a limiting fluence of ~0.15 Jy ms for broadband (3.3 GHz bandwidth) bursts or ~1 Jy ms for narrowband (64 MHz bandwidth) bursts during our observation.

We would like to thank the ATNF staff, in particular James Green, for allocating the observation time.

References:
Agarwal, D., et al., FETCH: A deep-learning based classifier for fast transient classification, MNRAS, 479, 1661 (2020)
Barr, E., Peasoup: C++/CUDA GPU pulsar searching library, Astrophysics Source Code Library, record ascl:2001.014 (2020)
Barsdell, B. R., Advanced Architectures for Astrophysical Supercomputing PhD thesis, Swinburne Univ. Technology (2012)
Hobbs, G., et al., An ultra-wide bandwidth (704 to 4032 MHz) receiver for the Parkes radio telescope, PASA, 37, e012 (2020)
Kumar, P., et al., Extremely band-limited repetition from a fast radio burst source, MNRAS, 500, 2525 (2021)
Ransom, S. M., New search techniques for binary pulsars, PhD thesis, Harvard University (2001)