GCN Circular 21453
P Veres and C Meegan (both UAH) report on behalf of the Fermi GBM Team: "At 22:01:41.58 UT on 10 August 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170810A (trigger 524095306 / 170810918). which was also detected by the Swift/BAT (Gibson et al., GCN 21450) and Fermi LAT (Racusin at al., GCN 21452). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 60 degrees. The GBM light curve shows multiple pulses with a duration (T90) of about 137 s (50-300 keV). The time-averaged spectrum from T0-6.1 s to T0+67.6 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.79 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 267 +/- 34 keV. The event fluence (10-1000 keV) in this time interval is (1.0 +/- 0.6)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+38.4 s in the 10-1000 keV band is 2.6 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."