TITLE: GCN CIRCULAR NUMBER: 22965 SUBJECT: GRB 180718B: Fermi GBM detection DATE: 18/07/19 14:07:31 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 18:18:24.46 UT on 18 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180718B (trigger 553630709 / 180718763). which was also detected by the Fermi LAT (Racusin et al. 2018, GCN 22961). The GBM on-ground location is consistent with the LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 48 degrees. The GBM light curve shows a structured FRED-like peak with a duration (T90) of about 98 s (50-300 keV). The time-averaged spectrum from T0+0 s to T0+66 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.73 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 761 +/- 78 keV. A Band function also fits the spectrum with Epeak = 731 +/- 83 keV, alpha = -0.71 +/- 0.05,and beta = -2.79 +/- 0.73. The event fluence (10-1000 keV) in this time interval is (2.6 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.6 s in the 10-1000 keV band is 3.6 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."