TITLE: GCN CIRCULAR NUMBER: 20913 SUBJECT: GRB 170318B: Fermi GBM observation DATE: 17/03/18 20:28:15 GMT FROM: Peter Veres at UAH P. Veres and C. Meegan (both UAH) report on behalf of the Fermi GBM Team: "At 15:27:53.09 UT on 18 March 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170318B (trigger 511543678 / 170318644). which was also detected by the Swift/BAT (Cholden-Brown et al. 2008, GCN 20908) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 93 degrees. The GBM light curve shows a single peak with a duration (T90) of about 4 s (50-300 keV). The time-averaged spectrum from T0-3.3 s to T0+1.8 s is adequately fit by a simple power law function with index -1.40 +/- 0.10. The event fluence (10-1000 keV) in this time interval is (8.0 +/- 1.4)E-7 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.8 s in the 10-1000 keV band is 1.9 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."