TITLE: GCN CIRCULAR NUMBER: 10431 SUBJECT: GRB 100218A : Fermi GBM detection DATE: 10/02/19 16:48:55 GMT FROM: David Tierney at UCD Dave Tierney (UCD) reports on behalf of the Fermi GBM Team: "At 04:38:45.93 UT on 18 February 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100218A (trigger 288160727 / 100218194). The on-ground calculated location, using the GBM trigger data, is RA = 206.6, DEC = -11.9 (J2000 degrees, equivalent to 13 h 46 m, -11 d 54 '), with an uncertainty of 2.2 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 37 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 30.8 +/- 1.6 s (8-1000 keV). The time-averaged spectrum from T0-4.1 s to T0+28.67 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -0.50 (+0.28/-0.25) and the cutoff energy, parameterized as Epeak, is 184.20 (+52.40/-29.70) keV (cstat 845 for 485 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.58 +/- 0.21)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.7 s in the 8-1000 keV band is 1.4 +/- 0.2 ph/s/cm^2. A Band function fits the spectrum equally well (cstat 840 for 484 d.o.f.) with Epeak= 131.60 (+32.70/-21.70) keV, alpha = -0.14 (+0.41/-0.33) and beta = -2.00 (+0.18/-0.30). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."