TITLE: GCN CIRCULAR NUMBER: 16787 SUBJECT: GRB 140906A - Fermi GBM Detection DATE: 14/09/07 09:55:02 GMT FROM: Oliver Roberts at UCD/Fermi O.J. Roberts (UCD), V. Pelassa and V. Connaughton (UAH) report on behalf of the Fermi GBM Team: At 04:11:38.70 UT on the 6th of September 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140906A (trigger 431669501/140906175). The angle from the Fermi LAT boresight is 90 degrees. The on-ground calculated location, using the GBM trigger data, is RA = 248.4, DEC = +49.5 (J2000 degrees, equivalent to +16h 33m, +49d 30'), with an uncertainty of 7.7 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). Early follow-up observations of the GBM location error box by the intermediate Palomar Transient Factory yielded two possible optical counterparts (Singer et al 2014, GCN 16786). The GBM light curve consists of a single peak followed by a fainter tail, with a duration (T90) of 39s (50-300 keV). The time-averaged spectrum from T0-6.1 s to T0+13.3 s (interval of brightest emission) is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 127 +/- 33 keV. The event fluence (10-1000 keV) in this time interval is (1.90 +/- 0.25)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+1.216 s in the 10-1000 keV band is 3.1 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog.