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GCN Circular 33672

GRB 230421: Swift/BAT-GUANO arcminute localization
2023-04-21T18:14:17Z (a year ago)
Aaron Tohuvavohu at University of Toronto <>
James DeLaunay (U Alabama), Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Samuele Ronchini (PSU), Tyler Parsotan (UMBC/GSFC) report:

Swift/BAT did not localize GRB 230431A onboard (T0: 2023-04-21 09:42:46.370000UTC, Fermi/GBM GCN 33668).

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 burst occured during a Swift slew. 
Slew mosaic imaging finds the position of the burst with SNR of 10.5.

The BAT position is
RA, Dec = 41.704, +1.119 deg which is
   RA(J2000)  = 02h 46m 48.96s
   Dec(J2000) = +01d 07′ 08.4″
with an estimated uncertainty of 5 arcmin radius.

The burst location is Sun constrained for Swift, so there will be no XRT or UVOT followup.

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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