TITLE: GCN CIRCULAR NUMBER: 10744 SUBJECT: GRB 100511A: Fermi GBM detection/observation DATE: 10/05/12 16:51:05 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH) report on behalf of the Fermi GBM Team: "At 00:49:56.23 UT on 11 May 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100511A (trigger 295231798 / 100511035). The Fermi Observatory executed a maneuver following this trigger and tracked the burst location for the next 5 hours, subject to Earth-angle constraints. The on-ground calculated location, using the GBM trigger data, is RA = 109.29, DEC = -4.65 (J2000 degrees, equivalent to 07 h 17.2 m, -4 d 39 '), with an uncertainty of 1.0 degree (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 43 degrees. The GBM light curve shows several pulses with a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-7.4 s to T0+52 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -1.32 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 946.6 (+134/-110) keV (C-stat 1777 for 863 d.o.f.). The event fluence (8-1000 keV) in this time interval is (7.08 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+25 s in the 8-1000 keV band is 8.81 +/- 0.18 ph/s/cm^2. A Band function fits the spectrum equally well (C-stat 1776 for 862 d.o.f.) with Epeak= 882.5 +166/-115 keV, alpha = -1.3 +/- 0.02 and beta = -2.43 (+0.24/-1.71). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."