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GCN Circular 32167

Subject
GRB 220606B: Swift/BAT-GUANO candidate arcminute localization of a short burst
Date
2022-06-06T12:23:36Z (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 220606B onboard (T0:
2022-06-06T01:03:28 UTC, Fermi/GBM GCN 32165).

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,
arXiv:2111.01769), detects the burst in a 0.512 s analysis time bin
with a sqrt(TS) of 10.7.
The duration of the burst as seen by BAT is less than 0.5 s.

A candidate arcminute localization is found with DeltaLLHOut of 11.3
and a DeltaLLHPeak of 3.1.
For this reason we can confidently claim detection, and preference for
an in FOV origin, but the best fit arcmin localization is not strongly
preferred over other positions.

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 = 28.474, -54.471 deg which is
   RA(J2000)  = 01h 53m 53.76s
   Dec(J2000) = -54d 28��� 15.6���
with an estimated uncertainty of 5 arcmin.

This position is consistent with the Fermi/GBM localization (GCN 32165).

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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