TITLE: GCN CIRCULAR NUMBER: 38091 SUBJECT: GRB 241105A: Swift/BAT-GUANO arcminute localization of a short burst DATE: 24/11/06 01:36:11 GMT FROM: Aaron Tohuvavohu at Caltech aaron.tohu@gmail.com

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

Swift/BAT did not localize GRB 241105A onboard (T0: 2024-11-05T16:06:04 UTC, Fermi GCN 38085).

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 position of the burst is found via BAT imaging with SNR of 11. The position is: RA, Dec = 66.2381, -49.7547 deg which is RA(J2000) = 04h 24m 57.14s Dec(J2000) = -49d 45′ 16.9″ with an estimated uncertainty of 3 arcmin radius.

This BAT-GUANO position is coincident with the optical transient discovered by GOTO (GCN 38088).

XRT and UVOT follow-up has been triggered. 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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