CHIME/FRB Detection of Three More Radio Bursts from SGR 1935+2154

ATel #14074; Deborah Good (University of British Columbia) on behalf of the CHIME/FRB collaboration
on 8 Oct 2020; 20:25 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Shriharsh Tendulkar (shriharsh@physics.mcgill.ca)

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On 2020 October 8, the CHIME Fast Radio Burst system (CHIME/FRB Collaboration et al. 2018 ApJ, 863, 48) detected three radio bursts from the direction of SGR 1935+2154, a Galactic magnetar known to emit bright millisecond-duration radio bursts (ATels #13681, #13684, #13699). The bursts were detected at 02:23:41.975, 02:23:43.924, and 02:23:44.878 UTC. These arrival times are referenced at the CHIME/FRB location (topocentric) and at a frequency of 400.1953125 MHz. The DM constant used is k_DM = 1.0 / 2.41e-4 MHz^-2 pc cm^-3 s^-1. The currently best-measured dispersion measures for the bursts are all ~332.7 pc/cc, consistent with previous detections of the source. The first and second bursts are separated by 0.954 s and the second and third bursts by 1.949 s, indicating that all three bursts occurred within one ~3.24 s SGR 1935+2154 rotation period (Israel et. al. 2016 MNRAS, 457, 4).

The first burst was detected in 23 out of the 1024 beams generated by the CHIME correlator, but the second was detected in only 2 beams and the third in only one. In the previous CHIME/FRB detection of SGR 1935+2154, the burst was detected in 93 CHIME/FRB beams. The primary burst was detected ~0.6 degrees off-meridian; the detection of multiple bursts close to transit suggests additional undetected activity. Burst dynamic spectra plots for the beams with the highest-S/N detection (uncorrected for the frequency-dependent beam response) are available at the URL provided below. Fluence estimates for all three events are still in progress and will be reported in a subsequent ATel.

Additional observations are strongly encouraged at all wavelengths.

Dynamic Spectra of the bursts