GCN Circular 10448
Colleen Wilson-Hodge (NASA) and Sylvain Guiriec (UAH) report on behalf of the Fermi GBM Team: "At 02:38:09.31 UT on 23 February 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100223A (trigger 288585491 / 100223110). The on-ground calculated location, using the GBM trigger data, is RA = 104.1, DEC = +2.8 (J2000 degrees, equivalent to 6 h 56 m, 2 d 48 '), with an uncertainty of 3.6 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 76 degrees. GBM triggered on a soft peak lasting about 0.05 s followed few ms later by a longer and harder one. The T90 duration is about 0.206 s (50-300 keV). The time-averaged spectrum from T0-0.01 s to T0+0.22 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -0.31 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 1143 +/- 109 keV (Castor C-stat 570.83 for 605 d.o.f.). The event fluence (10-1000 keV) in this time interval is (1.42 +/- 0.04)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.01 s in the 10-1000 keV band is 12.5 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."