TITLE: GCN CIRCULAR NUMBER: 20068 SUBJECT: GRB 161017A: Fermi GBM observation DATE: 16/10/18 05:00:56 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM C. M. Hui (NASA/MSFC) and C Meegan (UAH) report on behalf of the Fermi GBM Team: At 17:52:08.26 UT on 17 October 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 161017A (trigger 498419532/161017745), which was also detected by Swift (Troja et al., GCN 20064). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 125 degrees. The GBM light curve shows two peaks with a duration (T90) of about 32 s (50-300 keV). The time-averaged spectrum from T0-22.1 s to T0+8.6 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.04 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 298.50 +/- 45.00 keV The event fluence (10-1000 keV) in this time interval is (7.02 +/- 0.43)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.3 s in the 10-1000keV band is 5.6 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog.