GCN Circular 23666
C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 11:56:10.76 UT on 09 January 2019, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 190109B (trigger 568727775 / 190109497) which was also detected by the Swift (Sbarufatti et al. 2019, GCN 23648). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 46 degrees. The GBM light curve consists of a single peak with a duration (T90) of about 8 s (50-300 keV). The time-averaged spectrum from T0-6.1 s to T0+3.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.85 +/- 0.25 and the cutoff energy, parameterized as Epeak, is 92 +/- 14 keV. The event fluence (10-1000 keV) in this time interval is (6.76 +/- 0.67)E-7 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.6 s in the 10-1000 keV band is 2.8 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."