TITLE: GCN CIRCULAR NUMBER: 15975 SUBJECT: GRB 140311B: Fermi GBM Detection DATE: 14/03/12 20:40:40 GMT FROM: Matthew Stanbro at UAH/Fermi M. Stanbro (UAH) reports on behalf of the Fermi GBM Team: "At 21:14:35.65 UT on 11 March 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140311B (trigger 416265278/140311885), which was also detected by Swift (J. L. Racusin et al. 2014, GCN 15945). The GBM on-ground location, using the Fermi GBM trigger data, is consistent with the Swift/BAT location.The angle to the Fermi LAT boresight is 110 deg. from Swift location. The GBM light curve consists of several overlapping peaks with a combined duration (T90) of 72 s (50-300 keV). The time-averaged spectrum from T0-3 s to T0+69 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.5 +/- 0.1 and the high energy cutoff, parameterized as Epeak, is 117 +/- 8 keV. The event fluence (10-1000 keV) in this time interval is (7.9 +/- 0.4)E-06 erg/cm^2. The 1.0-sec peak photon flux measured starting from T0+0.6 s in the 10-1000 keV band is 3.2 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."