GCN Circular 33440
C. Malacaria (ISSI) reports on behalf of the Fermi GBM Team: "At 13:32:27.40 UT on 8 March 2023, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 230308A (trigger 699975152 / 230308564). The Fermi GBM Final Real-time Localization was reported in GCN 33420. The angle from the Fermi LAT boresight at the GBM trigger time is 42 degrees. The GBM light curve consists of a slightly structured main peak with a duration (T90) of about 0.6 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.64 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.52 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 943 +/- 46 keV. A Band function fits the spectrum equally well with Epeak= 907 +/- 52 keV, alpha = -0.51 +/- 0.03, beta = -3.1 +/- 0.4 . The event fluence (10-1000 keV) in this time interval is (8.5 +/- 0.2)E-06 erg/cm^2. The 0.064-sec peak photon flux measured starting from T0 in the 10-1000 keV band is 72 +/- 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/"