GCN Circular 33147
Subject
GRB 230102A: Swift/BAT-GUANO detection outside the coded FOV
Event
Date
2023-01-04T05:32:28Z (3 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
James DeLaunay (UAlabama), Gayathri Raman (PSU), Aaron Tohuvavohu (U
Toronto), Jamie A. Kennea (PSU) report:
Swift/BAT did not localize GRB 230102A onboard (T0:
2022-12-26T00:22:12 UTC, Fermi/GBM GCN 33137, AGILE GCN 33138,
GRBAlpha GCN 33143).
The Fermi 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ,
941, 169), detects the burst with a sqrt(TS) of 29.2 in a 0.128 s
analysis time bin.
NITRATES results indicate a burst coming from outside the coded FOV,
with DeltaLLHOut of -6.
See Section 9.1 and Figures 10 and 17 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/