TITLE: GCN CIRCULAR NUMBER: 30325 SUBJECT: GRB 210626A: Swift/BAT-GUANO detection and arcminute localization DATE: 21/06/26 15:32:38 GMT FROM: Aaron Tohuvavohu at U Toronto Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), Jamie A. Kennea (PSU), Gayathri Raman (PSU) report: Swift/BAT did not trigger on GRB 210626A (T0: 2021-06-26 08:16:15.9 UTC, Fermi/GBM GCN 30323). 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 greater than 20 seconds. The burst occurred during a Swift slew. Using the normal BAT imaging technique, we find the location for the GRB with an SNR of 7.6. The BAT position is RA, Dec = 221.6199, -1.1512 deg which is RA(J2000) = 14h 46m 28.78s Dec(J2000) = -1d 09′ 4.3″ with an estimated uncertainty of 5 arcmin. This position is consistent with the Ferm/GBM localization (GCN 30323). 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/