GCN Circular 33583
J. Wood (NASA/MSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 19:58:03 UT on 05 April 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230405B (trigger 702417488/230405832). which was also detected by the Swift/BAT and Swift/XRT (K. L. Page et al. 2023, GCN 33571). The Fermi GBM on-ground location is consistent with the Swift XRT position. The angle from the Fermi LAT boresight is 105 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 4.3 s (50-300 keV). The time-averaged spectrum from T0+0.0 to T0+5.1 s is best fit by a Band function with Epeak = 225 +/- 11 keV, alpha = -0.53 +/- 0.05, and beta = -2.4 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (1.2 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.5 s in the 10-1000 keV band is 27.5 +/- 0.5 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/"