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GCN Circular 31049

Subject
GRB 211106A: Swift/BAT-GUANO candidate arcminute localization of a short burst
Date
2021-11-06T14:51:34Z (3 years ago)
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 trigger on GRB 211106A (T0: 2021-11-06T04:37:31.2
UTC, INTEGRAL/SPI-ACS #9504).

The INTEGRAL 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:2111.01769Loading...
 
 ), confidently detects the burst in a 0.512 s analysis
time bin with a sqrt(TS) of 19.1.
Estimated T90 in the detector is 1.75 +/- 0.05 s (15-350 keV).

A candidate localization is found with DeltaLLHOut of 7.2 and a
DeltaLLHPeak of 6.7.
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.
Conventional imaging does not find a location for this burst.

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 = 343.643 -53.236 deg which is
   RA(J2000)  = 22h 54m 34.32s
   Dec(J2000) =  -53d 14��� 0.9���
with an estimated uncertainty of 7 arcmin.
The partial coding fraction at this position is 3.9%.

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/