TITLE: GCN CIRCULAR NUMBER: 19804 SUBJECT: GRB 160816730A: Fermi GBM detection/observation DATE: 16/08/17 00:41:06 GMT FROM: Bagrat Mailyan at UAH B. Mailyan (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 17:30:57.97 UT on 16 August 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160816730A (trigger 493061461 / 160816730), which was also detected by the LAT (Racusin et al., 2016, GCN 19802). The on-ground calculated location, using the GBM trigger data, is consistent with LAT position. The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software owing to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. The initial angle from the Fermi LAT boresight to the GBM ground location is 34 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 11.0 s (50-300 keV). The time-averaged spectrum from T0-0 s to T0+13.8 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.73 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 235 +/- 4.29 keV. A Band function fits the spectrum equally well with Epeak = 224 +/- 5.46 keV, alpha = -0.71 +/- 0.02 and beta = -2.97 +/- 0.19. The event fluence (10-1000 keV) in this time interval is (3.467 +/- 0.037)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+7.6 s in the 10-1000 keV band is 39.1 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."