[vsnet-grb-info 8446] GRB 090929A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9962
SUBJECT: GRB 090929A: Fermi GBM detection
DATE:    09/09/29 07:46:14 GMT
FROM:    Arne Rau at MPE  <arau at mpe.mpg.de>

Arne Rau (MPE)  
report on behalf of the Fermi GBM Team:

"At 04:33:03.97  UT on 29 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090929A (trigger 275891585  / 090929190).

The on-ground calculated location, using the GBM trigger
data, is RA = 51.7, DEC = -7.3 (J2000 degrees,
equivalent to 03h 27m, -07d 18'), with an uncertainty
of 1.3 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 122 degrees.

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

The GBM light curve consists of multiple short peaks
with a duration (T90) of about 8.5 +/- 0.4 s (8-1000 keV).
The time-averaged spectrum from T0+0.002s to T0+4.896s is
best fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.52 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 610.9 +/- 44.5 keV
(chi squared 439 for 393 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.06 +/- 0.03)E-05 erg/cm^2. The 1.822-sec peak photon flux measured
starting from T0+0.002 s in the 8-1000 keV band is 10.9 +/- 0.3 ph/s/cm^2.

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