TITLE: GCN CIRCULAR NUMBER: 11591 SUBJECT: GRB 110120A: Fermi GBM detection DATE: 11/01/21 16:23:22 GMT FROM: Lin Lin at UAH/NAOC Lin Lin (UAH) reports on behalf of the Fermi GBM Team: "At 15:59:39.23 UT on 20 January 2011, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 110120A (trigger 317231981 / 110120666). The on-ground calculated location, using the GBM trigger data, is RA = 64.54, DEC = -17.06 (J2000 degrees, equivalent to 04 h 18 m 09.6 s, -17 d 03 ' 36.0 "), with an uncertainty of 1.08 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 15 degrees. This burst triggered the Fermi spacecraft slew because of high peak flux. The GBM light curve shows a ~5 s peak followed by a ~40 s tail with a duration (T90) of about 27 s (50-300 keV). The time-averaged spectrum from T0+0.003 s to T0+43.393 s is acceptably fit by a power law function with an exponential high-energy cutoff. The power law index is -0.87 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 1156 +/- 172 keV (C-Stat 666.26 for 487 d.o.f.). The event fluence (10-1000 keV) in this time interval is (2.55 +/- 0.05)E-5 erg/cm^2. The 64 ms peak photon flux measured starting from T0+0.384 s in the 10-1000 keV band is 15.03 +/- 1.35 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."