GCN Circular 23095
C. Malacaria (NASA-MSFC/USRA), R. Hamburg (UAH), and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 22:38:59.66 UT on 06 August 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180806A (trigger 555287944 / 180806944). The event was also possibly detected by MASTER OT (Lipunov et al. 2018, GCN 23091) and COATLI (Watson et al. 2018, GCN 23092, GCN 23094) and triggered a Swift/XRT ToO (Evans et al. 2018, GCN 23093). The GBM on-ground location and the MASTER position are consistent. The angle from the Fermi LAT boresight at the GBM trigger time is 66 degrees. The GBM light curve consists of a single peak with a duration (T90) of about 15.6 +/- 0.8 s (50-300 keV). The time-averaged spectrum from T0-1.5 s to T0+16.9 s is best fit by a Band function with Epeak = 482.40 +/- 31.2, alpha index = -0.95 +/- 0.02 and beta index = -2.37 +/- 0.19. The event fluence (10-1000 keV) in this time interval is (2.197 +/- 0.039)E-05 erg/cm^2. The 1-sec peak photon flux Measured starting from T0+4.9 s in the 10-1000 keV band is 14.3 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."