[vsnet-grb-info 7057] GRB 081206: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8640
SUBJECT: GRB 081206: Fermi GBM detection
DATE:    08/12/08 16:10:09 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE) 
reports on behalf of the Fermi GBM Team: 

"At 06:35:53.02 UT on 06 December 2008, the Fermi Gamma-Ray Burst Monitor 
triggered and located GRB 081206 (trigger 250238154 / 081206275).

The on-ground calculated location, using the GBM trigger 
data, is RA = 120.1, DEC = 32.7  (J2000 degrees, 
equivalent to 08h 00m, 32d 42'), with an uncertainty 
of 5.2 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 102 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 24 s (8-1000 keV). 
The time-averaged spectrum from T0-6.144 s to T0+15.360 s is 
well fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.11 +/- 0.24 and
the cutoff energy, parameterized as Epeak, is 180 +/- 23 keV 
(chi squared 245 for 236 d.o.f.).
The event fluence (8-1000 keV) in this time interval is 
(4.0 +/- 0.6)E-06 erg/cm^2. The 1-sec photon flux measured 
starting from T0+3.072 s in the 8-1000 keV band 
is 2.4 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well 
(chi squared 242 for 235 d.o.f.) with Epeak= 151 +/- 29 keV, 
alpha = 0.13 +/- 0.37 and beta = -2.2 +/- 0.4. 

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