TITLE: GCN CIRCULAR NUMBER: 14583 SUBJECT: GRB 130504C: Fermi GBM detection DATE: 13/05/05 23:54:40 GMT FROM: Michael Burgess at UAH J. Michael Burgess (UAH), Valerie Connaughton (UAH) and Shaolin Xiong (UAH) report on behalf of the Fermi GBM Team: "At 23:28:57.518 UT on 04 May 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130504C (trigger 389402940 / 130504978). High peak flux from the GRB caused GBM to issue a repoint request that reoriented the satellite to place the GRB near the LAT boresight for 2.5 hours, subject to Earth limb contraints. The on-ground calculated location, using the GBM trigger data, is RA = 90.71, DEC = 4.45 (J2000 degrees, equivalent to 06 h 02 m, 4 d 27 '), with an uncertainty of 1.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). This location is consistent with the LAT location. The angle from the Fermi LAT boresight is 47 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of about 5 peaks associated with the GRB and 1 peak associated with a solar flare about 100 seconds prior to T0. The duration (T90) of the GRB is about 74 s (50-300 keV). The time-averaged spectrum from T0-2.0 s to T0+120.0 s is adequately fit by a Band function with Epeak = 637 +/- 34 keV, alpha = -1.23 +/- 0.01, and beta = -2.28 +/- 0.08 The event fluence (10-1000 keV) in this time interval is (1.34 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+30.8 s in the 10-1000 keV band is 43 +/- 0.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."