GCN Circular 9558
Arne Rau (MPE) reports on behalf of the Fermi GBM Team: "At 10:00:52.10 UT on 21 June 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090621C (trigger 267271254 / 090621417). The on-ground calculated location, using the GBM trigger data, is RA = 257.5 deg, DEC = -28.5 deg (J2000 degrees, equivalent to 17 h 10 m, -28 d 28 '), with an uncertainty of 3.3 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 52 degrees. The GBM light curve consists of multiple short peaks with a duration (T90) of about 59.9 s (8-1000 keV). The time-averaged spectrum from T0-3.072 s to T0+28.672 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -1.4 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 148 +/- 34 keV (chi squared 444 for 461 d.o.f.). The event fluence (8-1000 keV) in the above mentioned time interval is (1.8 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+4.096 s in the 8-1000 keV band is 2.29 +/- 0.06 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."