GCN Circular 33531
S. Dalessi (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 14:54:47.43 UT on 28 March 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 230328B (trigger 701708092 / 230328621), which was also detected by the Swift/BAT (J.D. Gropp et al. 2023, GCN 33527) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 38 degrees. The GBM light curve consists of a single burst with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-3.5 s to T0+19.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.16 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 169.6 +/- 9.9 keV. The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.3)E-06 erg/cm^2. The 1 sec peak photon flux measured starting from T0+1.4 s in the 10-1000 keV band is 12.7 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 125.0 +/- 11.3 keV, alpha = -1.03 +/- 0.06, and beta = -2.10+/- 0.09. 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/"