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GCN Circular 9933

GRB 090926: Fermi GBM detection
2009-09-26T14:27:11Z (15 years ago)
Elisabetta Bissaldi at MPE <>
Elisabetta Bissaldi (MPE) reports on behalf of the Fermi GBM Team:

"At 04:20:26.99 UT on 26 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090926 (trigger 275631628 / 090926181).
The on-ground calculated location, using the GBM trigger
data, is RA = 354.5, DEC = -64.2 (J2000 degrees,
equivalent to 23h 38m, -64d 12'), with an uncertainty
of 1.0 degree (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 48 degrees.
Moreover, this burst was bright enough to result in
a Fermi spacecraft repointing maneuver.

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

The GBM light curve consists of single pulse
with a duration (T90) of 20 +/- 2 s (8-1000 keV).
The time-averaged spectrum from T0 to T0+21 s is
best fit by a Band function with Epeak = 314 (+/- 4) keV,
alpha = -0.75 (+/-0.01) and beta = -2.59 (+0.04/-0.05)
(C-stat 1136 for 478 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.45 +/- 0.04)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3 s in the 8-1000 keV band
is 80.8 +/- 0.4 ph/s/cm^2.

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