GCN Circular 8912
A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 04:17:09.58 UT on 22 February 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090222 (trigger 256969031 / 090222179). The on-ground calculated location, using the GBM trigger data, is RA = 120.2, DEC = +43.4 (J2000 degrees, equivalent to 08h 01m, +43d 24'), with an uncertainty of 5.5 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 80 degrees. The GBM light curve shows one main peak with substructure with a duration (T90) of about 18 s (8-1000 keV). The time-averaged spectrum from T0-2.688 s to T0+14.720 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -1.00 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 157.7 +/- 19.8 keV (chi squared 523.89 for 480 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.19 +/- 0.19)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.528 s in the 8-1000 keV band is 1.10 +/- 0.14 ph/s/cm^2. A Band function fits the spectrum equally well (chi squared 522.58 for 479 d.o.f.) with Epeak= 147.9 +/- 27.1 keV, alpha = -0.97 +/- 0.14 and beta = -2.56 +/- 0.66. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."