TITLE: GCN CIRCULAR NUMBER: 36672 SUBJECT: GRB 240615A: Swift/BAT-GUANO arcminute localization of a short burst DATE: 24/06/16 01:36:09 GMT FROM: Aaron Tohuvavohu at University of Toronto aaron.tohu@gmail.com

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

Swift/BAT did not localize GRB 240615A onboard (T0: 2024-06-15T17:51:45 UTC, Fermi GCN 36671).

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 < 0.1 seconds. The burst occurred during a Swift slew. A confident location is found for the burst with SNR of 12.

The BAT position is RA, Dec = 326.1413, +38.5948 deg which is RA(J2000) = 21h 44m 33.91s Dec(J2000) = +38d 35’ 41.3″ with an estimated uncertainty of 4 arcmin.

This position is consistent with the Ferm/GBM localization (GCN 33023).

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/

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