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GCN Circular 32941

GRB 221115B: Swift/BAT-GUANO arcminute localization
2022-11-15T23:40:37Z (2 years ago)
Aaron Tohuvavohu at U Toronto <>
James DeLaunay (UAlabama), Aaron Tohuvavohu (U Toronto), Gayathri
Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (GSFC/UMBC) report:

Swift/BAT did not localize GRB 221115B onboard (T0:
2022-11-15T09:46:15 UTC, CALET trig 1352540756).

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 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 in a 2.048 s analysis time bin
with a sqrt(TS) of 27.7.
The duration of the burst as seen by BAT is ~5 seconds.

A confident arcminute localization is found with DeltaLLHPeak of 49.

See Section 9.1 and Figure 17 in the NITRATES paper for brief
descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and

The BAT position is
RA, Dec = 54.788, -16.701 deg which is
   RA(J2000)  = 03h 39m 09.16s
   Dec(J2000) = -16d 42��� 03.5���
with an estimated uncertainty of 3 arcmin.

XRT and UVOT follow-up has been requested, but will be significantly
delayed due to operational constraints.
We encourage followup from other facilities.

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:
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