TITLE: GCN CIRCULAR NUMBER: 32511 SUBJECT: GRB 220831A: Fermi GBM observation DATE: 22/09/01 17:55:47 GMT FROM: Joshua Wood at MSFC/Fermi-GBM J. Wood (NASA/MSFC) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 13:56:32.93 UT on 31 Aug 2022, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 220831A (trigger 683646997 / 220831581). which was also detected by the Swift/BAT-GUANO (A. Tohuvavohu et al. 2022, GCN 32506) The GBM on-ground location is consistent with the Swift position. The on-ground calculated location, using the GBM trigger data, is RA = 28.1, DEC = -45.1 (J2000 degrees, equivalent to 01h 52m, -45d 06'), with an uncertainty of 7.9 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 is 102.0 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 1.7 s (50-300 keV). The time-averaged spectrum from T0-0.5 s to T0+1.3 s is best fit by a Band function with Epeak = 46 +/- 8 keV, alpha = -0.67 +/- 0.45, and beta = -2.7 +/- 0.4 The event fluence (10-1000 keV) in this time interval is (5.0 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.2 s in the 10-1000 keV band is 9.4 +/- 1.7 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/"