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GCN Circular 9230

Subject
GRB 090424: Fermi GBM Observation
Date
2009-04-24T17:46:24Z (15 years ago)
From
Valerie Connaughton at MSFC <valerie@nasa.gov>
Valerie Connaughton (UAH) reports on behalf of the Fermi GBM Team:

"At 14:08:12.67 UT on 24 April 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090424 (trigger 262275130 / 090424592).
which was also detected by the Swift-BAT
(J. Cannizzo et al. 2009, GCN 9223).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 71 degrees, increasing
after trigger time.

The GBM light curve shows an intense, multi-peaked
emission period lasting around 6 sec, tailing off
into smaller peaks until about 20 sec after trigger time,
followed by a smaller peak between 45-60 sec after the trigger.  
The duration (T90) between 8 and 1000 keV is about 52 sec.
 
The time-averaged spectrum of the peak from T0-0.3 s to T0+5.5 s is
best fit by a Band function with Epeak = 177 +/- 3 keV,
alpha = 0.90 +/- 0.02, and beta = -2.9 +/- 0.1

The event fluence (8-1000 keV) over the entire event (-0.3 s to 59 s) is
(5.2 +/- 0.1)E-05 erg/cm^2. The 0.128-sec peak photon flux measured
at 1.4 s in the 8-1000 keV band is 137 +/- 5 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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