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GCN Circular 8374

Subject
GRB 081009: Fermi GBM detection
Date
2008-10-14T16:15:25Z (16 years ago)
From
Andreas von Kienlin at MPE <azk@mpe.mpg.de>
A. von Kienlin (MPE), P.N. Bhat (UAH) and C.A. Wilson-Hodge (MSFC) 
report on behalf of the Fermi GBM Team: 

"At 03:20:58 UT on 9 October 2008, the Fermi GBM triggered 
and located GRB 081009 (trigger 245215259 / 081009140). 
The on-ground calculated location, using the GBM trigger 
data, is RA = 251.1, Dec = +17.1  (J2000 degrees, 
equivalent to 16h 44m, +17d 06'), 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 67 degrees.

This GRB has two isolated peaks: 

The first peak is about 9 sec long. The time-averaged 
spectrum (8-1000 keV) from T0-0.1 s to T0+7.9 s is 
best fit by a Band function with Epeak = 47.4+/-0.3 keV, 
alpha = 0.10+/-0.03, and beta = -3.42+/-0.04. 
The fluence (8-1000 keV) is (3.5+/-0.1)E-05 erg/cm^2. 
The quoted errors are statistical only, the true errors are 
significantly larger due to systematic effects around the 
Iodine K-edge energy (33.2 keV) for this very strong event.

The second peak is about 13 sec long. The time-averaged 
spectrum (8-1000 keV) from T0+37.4 s to T0+49.3 s is 
best fit by a Band function with Epeak = 20.7+/-0.2 keV, 
alpha = 0.2+/-0.1, and beta = -4.0+/-0.1. 
The fluence (8-1000 keV) is (8.3+/-1.3)E-06 erg/cm^2.

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