[vsnet-grb-info 8342] GRB 090902: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9865
SUBJECT: GRB 090902: Fermi GBM detection
DATE:    09/09/02 16:44:07 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs at mpe.mpg.de>

E. Bissaldi and A. von Kienlin (MPE)
report on behalf of the Fermi GBM Team: 


"At 09:38:05.49 UT on 2 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090902 (trigger 273577087 / 090902401).
The on-ground calculated location, using the GBM trigger
data, is RA = 291.0, DEC = 53.1 (J2000 degrees,
equivalent to 19h 24m, 53d 06'), with an uncertainty
of 3.8 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 82 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of a single peak
with a duration (T90) of about 1.2 s (8-1000 keV).
The time-averaged spectrum from T0-0.256 s to T0+0.896 s is
best fit by a Band function with Epeak = 388 (+82/-102) keV,
alpha = 0.30 (+0.5/-0.26), and beta = -2.05 (+0.29/-0.24)
(chi squared 372 for 356 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(2.11 +/- 0.14)E-06 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+608 s in the 8-1000 keV band
is 11.4 +/- 1.3 ph/s/cm^2.


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