TITLE: GCN CIRCULAR NUMBER: 18126 SUBJECT: GRB 150810A: Fermi GBM detection DATE: 15/08/11 16:14:52 GMT FROM: Oliver Roberts at UCD/Fermi O.J. Roberts (UCD) reports on behalf of the Fermi GBM team: "At 11:38:08.91 on August 10th 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150810A (trigger 460899492/150810485). The GBM on-ground location, using the Fermi GBM trigger data, is RA = 283.20, Dec = +21.18 with an uncertainty of 3 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle of the burst direction to the Fermi LAT boresight is 62 degrees. The GBM light curve consists of two unresolved peaks with a duration of about 0.5s (50-300 keV). The time-averaged spectrum from T0-0.064s to T0+0.448s is best fit by a power law with an exponential high-energy cutoff. The power law index is -0.68 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1294 +/-159 keV. The event fluence (10-1000 keV) in this time interval is (1.87 +/- 0.04)E-06 erg/cm^2. The 64 ms peak photon flux measured starting from T0+0s in the 10-1000 keV band is 17.9 +/- 1.1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."