TITLE:   GCN CIRCULAR
NUMBER:  32095
SUBJECT: GRB 220514A: Swift/BAT-GUANO detection outside the coded FOV
DATE:    22/05/23 18:28:42 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), James DeLaunay
(UAlabama), Jamie A. Kennea (PSU), report:

Swift/BAT did not localize GRB 220514A onboard (T0:
2022-05-14T12:24:32 UTC, Fermi/GBM GCN 32038, INTEGRAL GCN 32041,
AstroSat GCN 32070, GECAM detection).

The Fermi, INTEGRAL, and GECAM 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 24.9 in a
16.384 s analysis time bin.
The burst episode as seen by BAT is >50 s long.

NITRATES results indicate a burst coming from outside the coded FoV,
with DeltaLLHOut of -29.7. The most likely sky position from NITRATES
agrees well with the INTEGRAL/IBAS position (GCN 32041).

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/