TITLE: GCN CIRCULAR NUMBER: 20943 SUBJECT: GRB 170329A: Fermi GBM detection DATE: 17/03/30 04:07:55 GMT FROM: Oliver J Roberts at USRA/NASA E.Bissaldi (Politecnico & INFN Bari), O.J.Roberts (USRA/MSFC) and C.Meegan (UAH) report on behalf of the Fermi GBM Team: "At 09:17:06.94 UT on 29 March 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170329A (trigger 512471831 / 170329387), which was also detected by the LAT (Yassine et al. 2017, GCN 20942) The GBM on-ground location is consistent with the LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 33 degrees. The GBM light curve consists of a bright peak with a duration (T90) of 33.5 s (50-300 keV). The time-averaged spectrum from T0+0 s to T0+33.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.61 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 799 +/- 86 keV The event fluence (10-1000 keV) in this time interval is (1.45 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.3 s in the 10-1000 keV band is 5.2 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."