TITLE: GCN CIRCULAR NUMBER: 21839 SUBJECT: GRB 170906A: Fermi GBM detection DATE: 17/09/06 21:32:38 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 00:43:08.15 UT on 06 September 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170906A (trigger 526351393 / 170906030), which was also detected by Swift (Siegel et al. 2017, GCN 21821). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 75 degrees. The GBM light curve shows a multi-peaked structure with a duration (T90) of about 79 s (50-300 keV). The time-averaged spectrum from T0-2.6 s to T0+107.0 is best fit by a Band function with Epeak = 288 +/- 12 keV, alpha = -1.02 +/- 0.02, and beta = -2.09 +/- 0.04. The event fluence (10-1000 keV) in this time interval is (1.17 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+33.4 s in the 10-1000 keV band is 21.7 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."