TITLE:   GCN CIRCULAR
NUMBER:  30130
SUBJECT: GRB 210605B: Swift/BAT-GUANO detection and arcminute localization
DATE:    21/06/06 00:21:21 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

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

Swift/BAT did not trigger on GRB 210605B (T0: 2021-06-06 14:55:58 UTC,
Fermi/GBM GCN 31029).

The Fermi/GBM 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 burst is detected in BAT with a duration of at least 20 seconds.
The burst occurred during a Swift slew.
The position of the burst was found with SNR of 8.4 using a novel slew
image mosaicing procedure (DeLaunay et al. 2021, in prep.), and so the
positional uncertainty is not yet well characterized.

The BAT position is
RA, Dec = 15.732, -6.467 deg which is
   RA(J2000)  = 01h 02m 55.68s
   Dec(J2000) =  -6d 28′ 1.2″
with an estimated uncertainty of 5 arcmin.

This position is consistent with the Ferm/GBM localization (GCN 31029).

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/