GCN Circular 22813
B. Mailyan (UAH) reports on behalf of the Fermi GBM Team: "At 15:50:36.05 UT on 20 June 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180620B (trigger 551202641 / 180620660), which was also detected by the Swift/BAT and XRT (Evans et al. 2018, GCN 22807). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 137 degrees. The GBM light curve shows multi-peaked structure with a duration (T90) of about 46.7 s (50-300 keV). Evans et al. 2018 report a shorter duration of ~30 s in the Swift/BAT. We suggest the discrepancy may be due to extended hard emission of this GRB. The time-averaged spectrum from T0 to T0+46 s is adequately fit a power law function with an exponential high-energy cutoff. The power law index is 0.85 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 149 +/- 11 KeV. A Band function fits the spectrum equally well with Epeak= 106 +/- 15 keV, alpha = -0.5 +/- 0.2 and beta = -2.2 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (7.7 +/- 0.04)E-06 erg/cm^2. The 1-s peak photon flux measured starting from T0 in the 10-1000 keV band is 6.8 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."