TITLE: GCN CIRCULAR NUMBER: 32556 SUBJECT: GRB 220909A: Fermi GBM observation DATE: 22/09/14 13:30:13 GMT FROM: Christian Malacaria at ISSI C. Malacaria (ISSI) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 06:52:13.82 UT on 9 September 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220909A (trigger 684399138 / 220909286), which was also detected by Swift/GUANO (Raman et al. 2022, GCN 32543). The Fermi GBM Final Real-time Localization (GCN 32539) is consistent with the Swift-BAT GUANO position. The angle from the Fermi LAT boresight at the GBM trigger time is 46 degrees. The GBM light curve shows a peak with a duration (T90) of about 14.6 s (50-300 keV). The time-averaged spectrum from T0-1.5 s to T0+6.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.8 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 154 +/- 25 keV. The event fluence (10-1000 keV) in this time interval is (1.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.69 s in the 10-1000 keV band is 3.6 +/- 0.2 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/"