TITLE: GCN CIRCULAR NUMBER: 16708 SUBJECT: GRB 140818A - Fermi GBM Detection DATE: 14/08/18 18:08:23 GMT FROM: Oliver Roberts at UCD/Fermi Oliver Roberts (UCD) reports on behalf of the Fermi GBM Team: "At 05:30:09.12 UT on the 18th of August 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140818A (trigger 430032612 / 140818229), which was also detected by MAXI/GSC (H. Negoro et al. GCN 16702 and GCN 16705). A possible afterglow has also been reported by Swift-XRT and UVOT (C. Swenson et al. GCN 16706) The GBM on-ground location is consistent with the MAXI/GSC and Swift positions. The angle from the Fermi LAT boresight is 35 degrees. The GBM light curve consists of two peaks, with the second peak at T~50s being brighter than the first. The duration (T90) of the burst is about 109 s (50-300 keV). The time-averaged spectrum from T0+25s to T0+135 s is adequately fit by a BAND function. The power law index alpha is -0.69 +/- 0.04 . The power law index beta is -2.39 +/- 0.10 . The cutoff energy, parameterised as Epeak, is 181 +/- 8 keV. The event fluence (10-1000 keV) in this time interval is (2.95 +/- 0.06)E-05 erg/cm^2. The 1.024-sec peak photon flux was measured starting from T0+99.5 s in the 10-1000 keV band is 8.6 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."