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GCN Circular 9849

GRB090829: Fermi GBM Detection
2009-08-31T01:54:07Z (15 years ago)
Colleen A. Wilson at NASA/MSFC/NSSTC <>
Colleen A. Wilson-Hodge reports on behalf of the Fermi GBM Team:

"At 16:07:38.86 UT on 29 August 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090829 (trigger 273254860 / 090829672).

The on-ground calculated location, using the GBM trigger data, is
RA = 329.2, DEC = -34.2 (J2000 degrees, equivalent to 21 h 57 m, 34 d 11'),
with an uncertainty of 1 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 47 degrees.
This burst triggered an automatic repoint of Fermi.

The GBM light curve, with a duration (T90) of about 85 s (8-1000 keV),
consists of a weak precursor followed by a bright peak. The
time-averaged spectrum from T0-6.1 s to T0+92 s is adequately fit by
a Band function with Epeak = 183 +/- 31 keV, alpha = -1.44 +/- 0.04,
and beta = -2.1 +/- 0.1

The event fluence (8-1000 keV) in this time interval is
(1.02 +/- 0.02)E-4 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+46 s in the 8-1000 keV band is 51.5 +/- 0.9 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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