TITLE: GCN CIRCULAR NUMBER: 30241 SUBJECT: GRB 210323B: Fermi GBM observation DATE: 21/06/16 17:23:38 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 12:03:33.09 UT on 23 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210323B (trigger 638193818/ 210323502), which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2021, GCN 29701). The Fermi GBM Final Real-time Localization is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 10 degrees. The GBM light curve consists of a weak emission episode with a duration (T90) of about 14 s (50-300 keV). The time-averaged spectrum from T0-4.9 s to T0+5.9 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.94 +/- 0.26 and the cutoff energy, parameterized as Epeak, is 740 +/- 540 keV. The event fluence (10-1000 keV) in this time interval is (2.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-4.5 s in the 10-1000 keV band is 1.1 +/- 0.2 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/"