TITLE: GCN CIRCULAR NUMBER: 22597 SUBJECT: GRB 180404B: Fermi GBM observation DATE: 18/04/04 10:04:46 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 02:11:38.64 UT on 04 April 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180404B (trigger 544500703 / 180404091), which was also detected by the Swift/BAT (LaPorte et al. 2018, GCN 22590). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 61.3 degrees. The GBM light curve shows a single bright peak followed by a secondary emission episode with a duration (T90) of about 80 s (50-300 keV). The time-averaged spectrum from T0+0.003 s to T0+33.281 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.40 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 209 +/- 6 keV. The event fluence (10-1000 keV) in this time interval is (3.3 +/- 0.4)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+12.86 s in the 10-1000 keV band is 8.0 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 204 +/- 8 keV, alpha = -0.38 +/- 0.04 and beta = -3.3 +/- 0.6. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."