GCN Circular 34290
S. Dalessi (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 02:50:05.24 UT on 28 July 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230728A (trigger 712205410/230728118). which was also detected by Swift BAT (Salvaggio et al. 2023, GCN 34282) and Swift XRT (Evans et al. 2023, GCN 34286). The Fermi GBM on-ground location is consistent with the Swift XRT position. The angle from the Fermi LAT boresight is 66 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-6.1 to T0+12.3 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 95 +/- 15 keV. The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-2.6 s in the 10-1000 keV band is 3.1 +/- 0.2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 78 +/- 20 keV, alpha = -1.1 +/- 0.3 and beta = -2.4 +/- 0.4. 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/"