GCN Circular 21840
R. Hamburg (UAH) and and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 00:55:40.85 UT on 06 September 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170906B (trigger 526352145 / 170906039). which was also detected by Swift (Sbarufatti et al. 2017, GCN 21822). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 53 degrees. The GBM light curve shows a two-peaked emission with a duration (T90) of about 12 s (50-300 keV). The time-averaged spectrum from T0-0.0 s to T0+12.8 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -1.11 +/- 0.13 and the cutoff energy, parameterized as Epeak, is 59 +/- 4 keV. The event fluence (10-1000 keV) in this time interval is (2.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+5.1 s in the 10-1000 keV band is 10.3 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."