GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
Abstract
Swift/BAT did not trigger on GRB 210323B (T0: 2021-03-23 12:03:33 UTC, Fermi/GBM TRIGGER 638193818). The Fermi/GBM notice, distributed in near real-time triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The burst is detected in BAT with a best fit duration of ~8 seconds. With a maximum likelihood analysis (DeLaunay et al. 2021, in prep.) on the event-mode data we detect a location for the burst with a square root of the test statistic, sqrt(TS), of 11.77. The sqrt(TS) behaves similarly to SNR. This is a low significance detection and it could not be recovered using the normal BAT imaging technique, so there is a chance that this localization may be incorrect. The BAT position is RA, Dec = 259.664, +15.677 deg which is RA(J2000) = 17h 18m 39.36s Dec(J2000) = +15d 40' 37.20" with an estimated uncertainty of 6 arcmin. The partial coding was 10.6% This position is consistent with the Fermi GBM localization. XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
- Publication:
-
GRB Coordinates Network
- Pub Date:
- March 2021
- Bibcode:
- 2021GCN.29701....1D