TITLE:   GCN CIRCULAR
NUMBER:  42245
SUBJECT: GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
DATE:    25/10/14 05:15:00 GMT
FROM:    Jimmy DeLaunay at Penn State <delauj2@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea
(PSU), Samuele Ronchini (GSSI), Gayathri Raman (PSU), Tyler Parsotan (GSFC), Maia Williams (Northwestern) report:

Swift/BAT did not localize GRB 251011A onboard (T0: 2024-10-11T03:41:40.09 UTC, Fermi GCN 42195, AstroSat CZTI GCN 42199, Insight-HXMT GCN 42210).

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 occurred during a Swift slew.
The arcmin position of the burst is found with the newly developed pipeline BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs (Ronchini et. al, in prep). The pipeline makes use of the tools from BatAnalysis (Parsotan et al. 2025).
A confident location is found for the burst with SNR of 23.5.
The burst is detected in BAT with a duration of ~ 5 seconds.

The BAT position is
RA, Dec = 4.7878, +45.1894 deg which is
   RA(J2000)  = 00h 19m 09.07s
   Dec(J2000) =  +45d 11’ 21.84″
with an estimated uncertainty of 5 arcmin.

This position is consistent with the Ferm/GBM localization (GCN 42195).

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/