[AAVSO-HEN] GRB 090926B: Fermi GBM detection

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  9957
SUBJECT: GRB 090926B: Fermi GBM detection
DATE:    09/09/28 01:34:51 GMT
FROM:    Michael S. Briggs at UAH and MSFC  <michael.briggs at nasa.gov>

Michael S. Briggs (UA Huntsville), reports on behalf of the Fermi GBM Team:

"At 21:55:28.53 UT on 26 Sept 2009, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 090926B (trigger 275694930  / 090926.914),
which also triggered the Swift BAT 19 seconds later (D. Grupe et al.,
GCN 9935).   The GBM location is consistent with the Swift BAT location.
The angle from the Fermi LAT boresight is approximately 100 degrees.

The GBM light curve shows multiple peaks with a duration (T90)
of 81 +/- 13 s (10 to 1000 keV). The time-averaged spectrum from T0 to
T0+48.6 s is best fit by cutoff power law with Epeak = 91 +/- 2 keV and 
index
= -0.13 +/- 0.06.   The fluence (10 to 1000 keV) in this time interval is
(8.7 +/- 0.3)E-06 erg/cm^2.

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