[AAVSO-HEN] GRB090107B: Fermi GBM Detection

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
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TITLE:   GCN CIRCULAR
NUMBER:  8793
SUBJECT: GRB090107B: Fermi GBM Detection
DATE:    09/01/09 23:33:40 GMT
FROM:    Adam Goldstein at Fermi-GBM/UAH  <adam.m.goldstein at msfc.nasa.gov>

A. Goldstein (UAH), R. Preece (UAH), and A.J. van der Horst (NASA/ORAU) 
report on behalf of the Fermi GBM Team: 

"At 16:20:42.77 UT on 07 January 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090107B (trigger 25303844 / 090107681).

This burst was also detected by the INTEGRAL IBAS
(D. Gotz et al. 2009, GCN 8786)
The GBM on-ground location is consistent with the INTEGRAL position.

The GBM light curve consists of two main emission peaks and apparent
substructure with a duration (T90) of about 24.1 s (8-1000 keV). 
The time-averaged spectrum from T0-4.1 s to T0+20.5 s is 
best fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.68 +/- 0.26 and
the cutoff energy, parameterized as Epeak, is 106.1 +/- 14.8 keV
(chi squared 530.4 for 486 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(1.75 +/- 0.37)E-06 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+6.1 s in the 8-1000 keV band 
is 3.68 +/- 0.27 ph/s/cm^2.

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