TITLE: GCN CIRCULAR NUMBER: 9424 SUBJECT: GRB 090524: Fermi GBM detection DATE: 09/05/26 15:20:47 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 08:17:56.23 UT on 24 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090524 (trigger 264845878 / 090524346). The on-ground calculated location, using the GBM trigger data, is RA = 329.5, DEC = -67.4 (J2000 degrees, equivalent to 21h 58m, 67d 24'), with an uncertainty of 1.3 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 63 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of two main pulses with a duration (T90) of about 72 s (8-1000 keV). The time-averaged spectrum from T0+0.003 s to T0+71.681 s is best fit by a Band function with Epeak = 82.6 +/- 6.3 keV, alpha = -1.00 +/- 0.08, and beta = -2.30 +/- 0.09 (chi squared 959 for 840 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.85 +/- 0.15)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+5.120 s in the 8-1000 keV band is 14.1 +/- 1.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."