GCN Circular 19411
O.J. Roberts (UCD), G. Fitzpatrick (UCD) and P. Veres (UAH) report on behalf of the Fermi GBM Team: "At 08:59:04.36 UT on 09 May 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160509A (trigger 484477148/160509374). The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software owing to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. The GRB was also detected by the LAT (F. Longo et al. 2016, GCN 19403), MAXI/GSC (Y. Ono et al. 2016, GCN 19404) and Swift XRT (J.A. Kennea et al. 2016, GCN 19408). The GBM on-ground location is consistent with these positions. The angle from the Fermi LAT boresight at the GBM trigger time using the LAT position, is 32 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 371 s (50-300 keV). The time-averaged spectrum from T0-1.5 s to T0+39.4 s is best fit by a BAND function, with Epeak = 370 +/- 7 keV, alpha = -0.89 +/- 0.01, and beta = -2.11 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (1.51 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+16.6 s in the 8-1000 keV band is 75.5 +/- 0.6 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."