GCN Circular 33758
O.J. Roberts (USRA/NASA-MSFC), S. Bala (USRA), C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 12:45:18.77 UT on 06 May 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 230506B (trigger 705069923 / 230506531), which was also detected by the Swift/BAT (S. Dichiara et al. 2023, GCN 33729 and S.D. Barthelmy et al. 2023, GCN 33742). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 47 degrees. The GBM light curve consists of multiple short bursts with a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-0.8 s to T0+39.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.28 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 1767 +/- 576 keV The event fluence (10-1000 keV) in this time interval is (1.13 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+10.4 s in the 10-1000 keV band is 8.1 +/- 0.3 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/"