[vsnet-grb-info 7353] GRB 090228: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8918
SUBJECT: GRB 090228: Fermi GBM detection
DATE:    09/02/28 17:42:15 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: 

"At 04:53:20.91 UT on 28 February 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located the bright short GRB 090228 (trigger 257489602 /
090228204).
The on-ground calculated location, using the GBM trigger 
data, is RA = 106.8, DEC = -24.3 (J2000 degrees, equivalent 
to 07h 07m, -24d 18'), with a statistical uncertainty of 
less than 1 degree (radius, 1-sigma containment) and an additional 
systematic error which is currently estimated to be 2 to 3 degrees.

The angle from the Fermi LAT boresight is 16 degrees

This short GRB shows a single bright pulse followed 
by a peak of significantly lesser intensity. 
The burst duration (T90) is about 0.8 s (8-1000 keV).
The time-averaged spectrum from T0-0.016 s to T0+0.176 s is 
best fit by a Band function with Epeak = 849 +/- 44 keV, 
alpha = -0.35 +/- 0.04, and beta = -2.98 +/- 0.25
(chi squared 732.29 for 723 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(6.1 +/- 0.09)E-06 erg/cm^2. The 0.32-sec peak photon flux measured 
starting from T0 s in the 8-1000 keV band is 133 +/- 8 ph/s/cm^2.

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