GRB 211206A: Swift/BAT-GUANO detection outside the coded FOV
Abstract
Swift/BAT detected a rate increase onboard (trigger ##1088092) but did not localize GRB 211206A (T0: 2021-12-06T19:51:10 UTC, AGILE/MCAL GCN 31175, CALET trig #1322855382). The CALET 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 90 seconds of BAT event-mode data from [-45,+45] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu, arXiv:2111.01769), detects the burst with a sqrt(TS) of 74.6 in a 4.096 s analysis time bin. Estimated T90 in the detector is 6.6 +/- 0.2 s (15-350 keV). NITRATES results strongly prefer an origin for the burst coming from outside the coded FOV, with DeltaLLHOut of -55.5. See Section 9.1 and Figure 20 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. 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:
- December 2021
- Bibcode:
- 2021GCN.31176....1D