GCN Circular 29626
S. Lesage (UAH), A. von Kienlin (MPE), C. Meegan (UAH), and C. Malacaria (NASA-MSFC/USRA) report on behalf of the Fermi GBM Team: "At 06:37:56.91 UT on 08 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210308A (trigger 636878281 / 210308276) which was also detected by the Swift/BAT and Swift/XRT (D'Elia et al. 2021, GCN 29619). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 26 degrees. The GBM light curve shows a single-peaked structure with a duration (T90) of about 5.4 s (50-300 keV). The time-averaged spectrum from T0-1.7 s to T0+7.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.82 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 142 +/- 5 keV. A Band function fits the spectrum equally well with Epeak = 135 +/- 7 keV, alpha = -0.78 +/- 0.05 and beta = -3.0 +/- 0.4. The event fluence (10-1000 keV) in this time interval is (6.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.1 s in the 10-1000 keV band is 20.0 +/- 0.4 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/"