TITLE: GCN CIRCULAR NUMBER: 16681 SUBJECT: GRB140809A: Fermi GBM observation DATE: 14/08/11 11:55:43 GMT FROM: Oliver Roberts at UCD/Fermi Oliver Roberts (UCD) and VĂ©ronique Pelassa (UAH) reports on behalf of the Fermi GBM Team: "At 03:11:10.20 UT on the 9th of August 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140809A (trigger 429246673 / 140809133), for which a possible optical transient was also detected by the MASTER II robotic telescope (Lipunov et al. 2014, GCN 16674). The GBM on-ground location is consistent with the OT position. The angle from the Fermi LAT boresight is 40 degrees. The GBM light curve consists of one bright pulse, followed by a sequence of shorter, dimmer pulses with a duration (T90) of about 70s (50-300 keV). The time-averaged spectrum from T0-14.6 s to T0+70.1 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.99 +/- 0.14 and the cutoff energy, parameterised as Epeak, is 507 +/- 192 keV. The event fluence (10-1000 keV) in this time interval is (2.10 +/- 0.04)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+1.28 s in the 10-1000 keV band is 1.39 +/- 0.18 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."