GCN Circular 9566
Arne Rau (MPE) reports on behalf of the Fermi GBM Team: "At 02:34:17.56 UT on 23 June 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090623 (trigger 267417259 / 090623107). The on-ground calculated location, using the GBM trigger data, is RA = 309.0deg, DEC = -43.2 deg (J2000 degrees, equivalent to 20 h 36 m, -43 d 12 '), with an uncertainty of 2.0 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 73 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of at least five peaks with a duration (T90) of about 72.2 s (8-1000 keV). The time-averaged spectrum from T0-1.920 s to T0+40.064 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -0.73 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 476 +/- 39 keV (chi squared 738 for 655 d.o.f.). The event fluence (8-1000 keV) in this time interval is (9.60 +/- 0.02)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+0.003 s in the 8-1000 keV band is 3.30 +/- 0.04 ph/s/cm^2. A Band function fits the spectrum equally well (chi squared 737 for 654 d.o.f.) with Epeak= 428 +/- 51 keV, alpha = -0.69 +/- 0.05 and beta = -2.3 +/- 0.4. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."