TITLE: GCN CIRCULAR NUMBER: 9508 SUBJECT: GRB 090610B: Fermi GBM detection DATE: 09/06/12 16:28:34 GMT FROM: Adam Goldstein at Fermi-GBM/UAH A. Goldstein (UAH) reports on behalf of the Fermi GBM Team: "At 17:21:31.90 UT on 10 June 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090610B (trigger 266347293 / 090610723). The on-ground calculated location, using the GBM trigger data, is RA = 276.0, DEC = -42.1 (J2000 degrees, equivalent to 18h 24m, -42d 06'), with an uncertainty of 9.5 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 91 degrees. The GBM light curve consists of a single short pulse at trigger time followed by a broad pulse starting at T0+80 s with a total duration (T90) of about 202.5 s (8-1000 keV). The time-averaged spectrum for the first pulse from T0-6.2 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 -0.46 +/- 0.36 and the cutoff energy, parameterized as Epeak, is 104.90 +/- 16.70 keV (chi squared 338.8 for 359 d.o.f.). The time-averaged spectrum for the second pulse from T0+79.9 s to T0+161.8 s is best fit by a simple power law function with index -1.66 +/- 0.07 (chi squared 454.9 for 360 d.o.f.). The event fluence (8-1000 keV) in the total time interval is (4.13 +/- 0.24)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.0 s in the 8-1000 keV band is 1.54 +/- 0.43 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."