TITLE: GCN CIRCULAR NUMBER: 9425 SUBJECT: GRB 090522 : Fermi GBM detection DATE: 09/05/27 12:46:59 GMT FROM: Sheila McBreen at MPE Sheila McBreen (UCD/MPE) and Andreas von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 08:15:49.33 UT on 22 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090522 (trigger 264672951 / 090522344). The on-ground calculated location, using the GBM trigger data, is RA = 277.7, DEC = +19.6 (J2000 degrees, equivalent to 18 h 31 m, +19 d 36 '), with an uncertainty of 4.9 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 53 degrees. The GBM light curve consists of one pulse with a duration (T90) of about 22 s (8-1000 keV). The time-averaged spectrum from T0-2 s to T0+20 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -1.03 (+ 0.41 / -0.53) and the cutoff energy, parameterized as Epeak, is 75.8 (+36.9 / -15.9) keV (chi squared 615 for 603 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.2 +/- 0.3)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2 s in the 8-1000 keV band is 3.5 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."