GCN Circular 10187

David Gruber (MPE) reports on behalf of the Fermi GBM Team: 


"At 04:34:40.23  UT on 20 November 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 091120 (trigger 280384482 / 091120191).

The on-ground calculated location, using the GBM trigger 
data, is RA = 224.8, DEC = -24.8 (J2000 degrees, 
equivalent to 14h 59m, -24d 48'), with an uncertainty 
of 1.32 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 45 degrees.
Moreover, this burst was bright enough to result in
a Fermi spacecraft repointing maneuver.

The GBM light curve consists of several peaks with a 
duration (T90) of about 52 s (8-1000 keV). 
The time-averaged spectrum from T0-3 s to T0+56 s is 
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.17 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 129 +/- 3 keV.
(C-stat 691 for 362 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(3.02 +/- 0.04)E-5 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+26.6 s in the 8-1000 keV band 
is 21.3 +/- 0.4 ph/s/cm^2.

A Band function fits the spectrum equally well (C-stat 687 for 361 d.o.f.) 
with Epeak= 124 +/- 4 keV, alpha = -1.15 +/- 0.02 
and beta = -2.98 +/- 0.27. 

The spectral analysis results presented above are preliminary; 
final results will be published in the GBM GRB Catalog."