[vsnet-grb-info 8233] GRB 090809B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9760
SUBJECT: GRB 090809B: Fermi GBM detection
DATE:    09/08/10 15:22:19 GMT
FROM:    Alexander van der Horst at NASA/MSFC  <Alexander.J.VanDerHorst at nasa.gov>

A.J. van der Horst (NASA/MSFC/ORAU) reports on behalf of the Fermi GBM 
Team:

"At 23:28:14.61 UT on 9 August 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090809B (trigger 271553296 / 090809978).
The on-ground calculated location, using the GBM trigger data, is
RA = 95.3, DEC = 0.1 (J2000 degrees, equivalent to 6h21m, +0d08'),
with an uncertainty of 1.2 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 81 degrees.

The GBM light curve consists of a single pulse with a duration (T90)
of about 15 s (8-1000 keV).
The time-averaged spectrum from T0 to T0+14.3 s is best fit by a Band
function with Epeak = 198 +/- 13 keV, alpha = -0.85 +/- 0.04, and
beta = -2.02 +/- 0.06 (chi squared 552 for 484 d.o.f.).
The event fluence (8-1000 keV) in this time interval is
(2.26 +/- 0.03)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.1 s in the 8-1000 keV band is 23.6 +/- 0.5 ph/s/cm^2.

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