GRB 220222A: Swift/BAT-GUANO detection outside the coded FOV
Abstract
Swift/BAT did not localize GRB 220222A onboard (T0: 2022-02-22T02:21:17 UTC, Fermi/GBM GCN 31630, CALET trigger #1329531683). The Fermi and CALET notices, 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu, arXiv:2111.01769), detects the burst with a sqrt(TS) of 17.2 in a 2.048 s analysis time bin. The observed duration of the burst is ~5 s. NITRATES results are consistent with a burst coming from outside the coded FOV, with DeltaLLHOut of -7. The best fit out of FoV location is consistent with the Fermi/GBM localization (GCN 31630). 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:
- February 2022
- Bibcode:
- 2022GCN.31633....1T