[vsnet-grb-info 7904] GRB 090528B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9447
SUBJECT: GRB 090528B: Fermi GBM detection
DATE:    09/05/30 15:35:59 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 12:22:31.29 UT on 29 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090528B (trigger 265206153 / 090528516).
The on-ground calculated location, using the GBM trigger 
data, is RA = 312.2, DEC = 32.7 (J2000 degrees, 
equivalent to 20h 49m, 32d 42'), 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 65 degrees.

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

The GBM light curve shows a strong multiple peak event follwed by 
a weaker structered tail with a duration (T90) of about 102 s (8-1000 keV). 
The time-averaged spectrum from T0-2.048 s to T0+57.345 s is 
best fit by a Band function with Epeak = 172 +/- 12  keV, 
alpha = -1.10 +/- 0.04, and beta = -2.3 +/- 0.1
(chi squared 516 for 477 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(4.65 +/- 0.15)E-05 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+9.216 s in the 8-1000 keV band 
is 14.7 +/- 1.3 ph/s/cm^2.

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