[vsnet-grb-info 7408] GRB090305B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8972
SUBJECT: GRB090305B: Fermi GBM detection
DATE:    09/03/10 17:50:24 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 01:14:35.72 UT on 05 March 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090305B (trigger 257908477 / 090305052).

The on-ground calculated location, using the GBM trigger data, is
RA = 155.1, DEC = 68.1 (J2000 degrees, equivalent to 10 h 20 m, 68 d 06'),
with an uncertainty of 5.4 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 40 degrees.

The GBM light curve shows/consists of a single peak with a duration (T90)
of about 2 s (8-1000 keV). The time-averaged spectrum from T0-0.5 s to
T0+2.5 s is best fit by a Band function with Epeak =  770+/- 230 keV,
alpha = -0.50 +/- 0.17, and beta = -1.9 +/- 0.2.

The event fluence (8-1000 keV) in this time interval is
(2.7 +/- 0.2)E-06 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+0.288 s in the 8-1000 keV band is 11 +/- 2 ph/s/cm^2.

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