[vsnet-grb-info 6689] GRB 080920: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8290
SUBJECT: GRB 080920: Fermi GBM detection
DATE:    08/09/25 13:55:36 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE), E. Bissaldi (MPE), S. McBreen (MPE) 
report on behalf of the Fermi GBM Team: 

"At 06:25:48 UT on 20 September 2008, the Fermi Gamma-ray Burst Monitor
triggered and located GRB 080920 (trigger 243584749 / 080920268). 
The on-ground calculated location using the Fermi GBM trigger data is 
RA = 124.6, Dec = 1.6 (equivalent to J2000 08h 18m, 01d 36'), 
with a statistical uncertainty of 3.4  degrees 
(radius, 1-sigma containment; there is additionally a systematic 
error which is currently estimated to be 2 to 3 degrees). 
The angle from the Fermi LAT boresight is 16 degrees.

This long GRB comprises one FRED like pulse, starting at T0-6 s.
T90 (25-1000 keV) is about 85 s. The time-averaged spectrum 
from T0-6 to T0+79 s is adequately fit by a power law model 
with index -1.42 +/- 0.06. It can also be fit with a power 
law function with an exponential high energy cutoff. 
The cutoff energy, parameterized as Epeak, is 162 +/- 35 keV. 
In this case the power law index is poorly constrained (-0.63 +/- 0.25).


The fluence in the 25-1000 keV band is 2.4 (+/- 0.5) E-06 erg/cm2 
and the peak flux (25-1000 keV) on the 1 s timescale
is 1.29 (+/- 0.14) ph/cm2/s.  

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