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GCN Circular 32345

Subject
GRB 220708B: Swift/BAT-GUANO arcminute localization
Date
2022-07-08T10:11:30Z (2 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
Aaron Tohuvavohu (U Toronto), James DeLaunay (UAlabama), Gayathri
Raman (PSU), Jamie A. Kennea (PSU), report:

Swift/BAT did not localize GRB 220708B onboard (T0:
2022-07-08T02:06:67 UTC, CALET trig #1341281218).

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 in a 4.096 s analysis time bin
with a sqrt(TS) of 41.4.
The duration of the burst as seen by BAT is ~7 seconds.

A confident arcminute localization is found with DeltaLLHOut of 150
and a DeltaLLHPeak of 68.

See Section 9.1 and Figure 20 in the NITRATES paper for brief
descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and
DeltaLLHOut.

The BAT position is
RA, Dec = 248.652, 36.338 deg which is
   RA(J2000)  = 16h 34m 36.48s
   Dec(J2000) = +36d 20��� 16.8���
with an estimated uncertainty of 5 arcmin.

XRT and UVOT follow-up has been requested
Results of follow-up observations will be reported in future circulars.

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/
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