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."