GCN Circular 31906
E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 07:28:04.65 UT on 8 April 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220408B (trigger 671095689 / 220408311), which was also detected by the AstroSat CZTI (Gopalakrishnan et al. 2022, GCN 31863), Fermi-LAT (Bissaldi et al. 2022, GCN 31896), and Konus-Wind (Lysenko et al. 2022, GCN 31905). The Fermi GBM Final Localization (GCN 31854) is consistent with the LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 29 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 33 s (50-300 keV). The time-averaged spectrum from T0 to T0+33 s is best fit by a Band function with Epeak = 214 +/- 8 keV, alpha = -0.80 +/- 0.02 and beta = -2.33 +/- 0.09. The event fluence (10-1000 keV) in this time interval is (3.68 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.6 s in the 10-1000 keV band is 17.1 +/- 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/"