TITLE: GCN CIRCULAR NUMBER: 9392 SUBJECT: GRB 090518B: Fermi GBM detection DATE: 09/05/18 14:45:29 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 05:51:04.67 UT on 18 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090518B (trigger 264318666 / 090518244). The on-ground calculated location, using the GBM trigger data, is RA = 211.2, DEC = -16.7 (J2000 degrees, equivalent to 14h 05m, -16d 42'), with an uncertainty of 4.5 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 90 degrees. The GBM light curve shows one structured peak with a duration (T90) of about 12 s (8-1000 keV). The time-averaged spectrum from T0-0.768 s to T0+6.656 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.74 +/- 0.13 and the cutoff energy, parameterized as Epeak, is 127 +/- 12 keV (chi squared 399 for 363 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.256 s in the 8-1000 keV band is 5.6 +/- 0.6 ph/s/cm^2. The spectrum can also be fit by using a Band function with Epeak = 86 +/- 15 keV and beta = -2.10 +/- 0.14. However alpha is poorly constrained. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."