TITLE: GCN CIRCULAR NUMBER: 32824 SUBJECT: GRB 221022A: Swift/BAT-GUANO detection DATE: 22/10/24 02:41:40 GMT FROM: Aaron Tohuvavohu at U Toronto Aaron Tohuvavohu (U Toronto), Gayathri Raman (PSU), James DeLaunay (UAlabama), Jamie A. Kennea (PSU), Tyler Parsotan (GSFC/UMBC) report: Swift/BAT did not localize GRB 221022A onboard (T0: 2022-10-22T19:33:33 UTC, Fermi/GBM GCN 32816). 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, 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu, arXiv:2111.01769), detects the burst with a sqrt(TS) of 8.7 in a 4.096 s analysis time bin. NITRATES results, independently, are ambiguous with respect to whether this burst originates from in or outside the BAT FOV, with a borderline DeltaLLHOut of 9.5. The best fit In FOV position is very weakly preferred over other positions, with DeltaLLHPeak of 2.1. This position is consistent with the Fermi/GBM localization (GCN 32816). The candidate position is RA, Dec = 118.342, -5.117 which is RA(J2000) = 07h 53m 22.03s Dec(J2000) = -5d 07′ 00.9″ with an estimated uncertainty of 5 arcmin. See Section 9.1 and Figure 20 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. 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/