TITLE: GCN CIRCULAR NUMBER: 16700 SUBJECT: GRB 140817A: Fermi GBM Detection DATE: 14/08/17 18:48:16 GMT FROM: Oliver Roberts at UCD/Fermi Oliver Roberts (UCD) and Charles Meegan (UAH) report on behalf of the Fermi GBM Team: "At 07:01:58.19 UT on the 17th of August 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140817A (trigger 429951721 / 140817293), which was also detected by the BAT and XRT on Swift (Sbarufatti et al., Evans et al. and Cummings et al. 2014, GCNs 16695-99). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 124 degrees. The GBM light curve consists of two bright peaks with a duration (T90) of about 16 s (50-300 keV). The time-averaged spectrum from T0-9 s to T0+16 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.64 +/- 0.19 and the cutoff energy, parameterised as Epeak, is 130 +/- 11 keV. The event fluence (10-1000 keV) in this time interval is (5.03 +/- 0.04)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+5.8 s in the 10-1000 keV band is 10.6 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."