GCN Circular 10449
S. Foley (MPE) and S. McBreen (UCD/MPE) report on behalf of the Fermi GBM Team: "At 02:45:31.15 UT on 25 February 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100225A (trigger 288758733 / 100225115). The on-ground calculated location, using the GBM trigger data, is RA = 312.5, DEC = -54.9 (J2000 degrees, equivalent to 20 h 50 m, -54 d 54 '), with an uncertainty of 2.4 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 58 degrees. The GBM light curve consists of two main pulses with a duration (T90) of about 13 (+/-3) s (50-300 keV) starting at -0.256 s. The time-averaged spectrum from T0-3.8 s to T0+13.6 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.80 (+0.09/-0.08) and the cutoff energy, parameterized as Epeak, is 527.30 (+105.00/-76.10) keV (CSTAT 438 for 361 d.o.f.). The event fluence (8-1000 keV) in this time interval is (7.6 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.4 s in the 8-1000 keV band is 4.13 +/- 0.20 ph/s/cm^2. A Band function fits the spectrum equally well (CSTAT 436 for 360 d.o.f.) with Epeak= 428.00 (+130.00/-86.00) keV, alpha = -0.72 (+0.13/-0.12) and beta = -2.15 (+0.21/-0.75). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."