TITLE: GCN CIRCULAR NUMBER: 9447 SUBJECT: GRB 090528B: Fermi GBM detection DATE: 09/05/30 15:35:59 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 12:22:31.29 UT on 29 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090528B (trigger 265206153 / 090528516). The on-ground calculated location, using the GBM trigger data, is RA = 312.2, DEC = 32.7 (J2000 degrees, equivalent to 20h 49m, 32d 42'), with a statistical uncertainty of less than 1 degree (radius, 1-sigma containment) and an additional systematic error which is currently estimated to be 2 to 3 degrees. The angle from the Fermi LAT boresight is 65 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve shows a strong multiple peak event follwed by a weaker structered tail with a duration (T90) of about 102 s (8-1000 keV). The time-averaged spectrum from T0-2.048 s to T0+57.345 s is best fit by a Band function with Epeak = 172 +/- 12 keV, alpha = -1.10 +/- 0.04, and beta = -2.3 +/- 0.1 (chi squared 516 for 477 d.o.f.). The event fluence (8-1000 keV) in this time interval is (4.65 +/- 0.15)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+9.216 s in the 8-1000 keV band is 14.7 +/- 1.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."