TITLE: GCN CIRCULAR NUMBER: 15977 SUBJECT: GRB 140311C: Fermi GBM Detection DATE: 14/03/12 22:28:45 GMT FROM: Matthew Stanbro at UAH/Fermi M. Stanbro (UAH) reports on behalf of the Fermi GBM Team: "At 14:49:13.10 UT on 11 March 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140311C (trigger 416242156/140311618). iPTF reported an optical counterpart candidate for this source (L.P. Singer et al. 2014, GCN 15971). The GBM on-ground location, using the Fermi GBM trigger data, is RA = 183.7 , DEC = +62.81 (J2000 degrees, equivalent to 12h 14m, 62d 48'), with an uncertainty of 3 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle to the Fermi LAT boresight is 53 deg. The GBM light curve consists of single peak with a duration (T90) of 14 s (50-300 keV). The time-averaged spectrum from T0-2 s to T0+12 s is well fit by a Band function parameterized as Epeak = 56 +/- 6 keV, alpha = -0.9 +/- 0.16 and beta = -2.4 +/- 0.12. The event fluence (10-1000 keV) in this time interval is (4.6 +/- 0.2)E-06 erg/cm^2. The 1.0-sec peak photon flux measured starting from T0+0.3 s in the 10-1000 keV band is 10.7 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."