TITLE: GCN CIRCULAR NUMBER: 9399 SUBJECT: GRB 090511: Fermi GBM Detection DATE: 09/05/19 20:48:51 GMT FROM: Valerie Connaughton at MSFC Valerie Connaughton (UAH) reports on behalf of the Fermi GBM Team: "At 16:25:16.37 UT on 11 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090511 (trigger 263751918 / 090511684). The on-ground calculated location, using the GBM trigger data, is RA = 161.9, DEC = 51.3 (J2000 degrees, equivalent to 10 h 48 m, 51 d 18 '), with an uncertainty of 7.0 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 from the Fermi LAT boresight is 67 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 14 s (8-1000 keV). The time-averaged spectrum from T0-5.1 s to T0+4.1 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -0.95 +/- 0.18 and the cutoff energy, parameterized as Epeak, is 391 +/- 157 keV. The event fluence (8-1000 keV) in this time interval is (1.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1 s in the 8-1000 keV band is 2.5 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."