[vsnet-grb-info 8298] GRB 090817: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9823
SUBJECT: GRB 090817: Fermi GBM observation
DATE:    09/08/17 18:23:30 GMT
FROM:    Colleen A. Wilson at NASA/MSFC/NSSTC  <colleen.wilson at nasa.gov>

Colleen A. Wilson-Hodge (NASA/MSFC)
reports on behalf of the Fermi GBM Team:

"At 00:51:26.21 UT on 17 August 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090817 (trigger 272163088 / 090817036).
which was also detected by INTEGRAL (Beckmann et al. 2009, GCN 9815)
The GBM on-ground location is consistent with the INTEGRAL position.
 
The angle from the Fermi LAT boresight is 82 degrees.

The GBM light curve consists of an initial bright peak at the trigger time
followed by a weak broad bump about 200 s after the trigger. This burst has
a duration (T90) of about 220 s (8-1000 keV).

Spectral analysis was performed only for the bright initial peak. The
time-averaged spectrum from T0 to T0+41 s is adequately fit by a Band
function with Epeak = 115 +/- 50 keV, alpha = -1.1 +/- 0.3, and
beta = -2.2 +/- 0.6

The event fluence (8-1000 keV) over the T90 interval is
(7.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.15 s in the 8-1000 keV band
is 3.8 +/- 0.3 ph/s/cm^2.

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