//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32476 SUBJECT: GRB 220823A: Swift/BAT-GUANO detection of a short burst DATE: 22/08/23 15:23:02 GMT FROM: Aaron Tohuvavohu at U Toronto Aaron Tohuvavohu (U Toronto), James DeLaunay (UAlabama), Gayathri Raman (PSU), Jamie A. Kennea (PSU), report: Swift/BAT did not localize GRB 220823A onboard (T0: 2022-08-23T03:28:52 UTC, Fermi/GBM trig #682918137). 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 [-45,+45] 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 13.4 in a 1.024 s analysis time bin. The duration of the burst as seen by BAT is T90~1.4 s. NITRATES results, independently, are ambiguous with respect to whether this burst originates from in or outside the BAT FOV, with a borderline DeltaLLHOut of 9.9 and no specific location in the FOV significantly preferred. Effort to localize this burst will continue. Independent spectral and/or fluence measurements of this burst from other instruments could help determine the preferred spatial origin. 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/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32479 SUBJECT: GRB 220823A: Fermi GBM detection DATE: 22/08/24 16:43:38 GMT FROM: Boyan A. Hristov at UAH B. Hirstov (UAH) and C. Fletcher (USRA) report on behalf of the Fermi GBM Team: "At 03:28:52.39 UT on 23 August 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220823A (trigger 682918137 / 220823145),which was also detected by Swift/BAT-GUANO (A. Tohuvavohu et al. 2022, GCN 32476). The on-ground calculated location, using the GBM trigger data, is RA = 82.94, DEC = +2.44 (J2000 degrees, equivalent to 05h, 31m, 2d 26'), with a statistical uncertainty of 3 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ). The angle from the Fermi LAT boresight at the GBM trigger time is 15 degrees. The GBM light curve consists of single peak with a duration (T90) of 1.1 +/- 0.7 s (50-300 keV). The time-averaged spectrum from T0-1.024 s to T0+0.256 s is best fit by a power law with an exponential cutoff with Epeak = 1189 +/- 608 keV and alpha = -0.52 +/- 0.26. The event fluence (10-1000 keV) in this time interval is (1.1 +/- 0.1)E-6 erg/cm^2. The 0.064-sec peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 5 +/- 1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"