[vsnet-grb-info 7822] GRB 090509: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9366
SUBJECT: GRB 090509: Fermi GBM observation
DATE:    09/05/15 15:33:09 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE) and Sheila McBreen (UCD/MPE) 
report on behalf of the Fermi GBM Team: 

"At 05:10:05.72 UT on 09 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090509 (trigger 263538607 / 090509215)
which was also detected by the SWIFT-BAT (Grupe et al. 2008, GCN 9325; 
Krimm et al., GCN 9349). The GBM on-ground location is consistent 
with the Swift position.

The angle from the Fermi LAT boresight is 75 degrees.

The GBM light curve consists of two widely separated multi-peaked 
emission periods with a duration (T90) of about 295 s (8-1000 keV). 
The time-averaged spectrum of the first emission complex from 
T0-3.072 to T0+24.576  s is well fit by a power law function with 
an exponential high energy cutoff.  The power law index is -0.90 +/- 0.16 
and the cutoff energy, parameterized as Epeak, is 343 +/- 93 keV 
(chi squared 375 for 360 d.o.f.). 
The time-averaged spectrum of the second emission complex from 
T0+239.619 s to T0+288.772 s is best fit by a simple power 
law function with index -1.55 +/- 0.07 (chi squared 328 for 361 d.o.f.).

The summed event fluence (8-1000 keV) of both time intervals is 
(8.4 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+18.432 s in the 8-1000 keV band 
is 3.1 +/- 0.3  ph/s/cm^2.

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