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GCN Circular 9131

Subject
GRB 090411B: Fermi GBM detection
Date
2009-04-16T14:39:32Z (15 years ago)
From
Rob Preece at UAH <Rob.Preece@nasa.gov>
Rob Preece (UAH) reports on behalf of the Fermi GBM Team:

"At 23:47:44.88 UT on 11 April 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090411B (trigger 261186466 / 090411991).

The on-ground calculated location, using the GBM trigger
data, is RA = 37.0, DEC = 3.2 (J2000 degrees,
equivalent to 02 h 28 m, 3 d 15 '), with an uncertainty
of 2.8 degrees (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 111 degrees.

The GBM light curve consists of a single spiky outburst
with a duration (T90) of about 18.7 s (8-1000 keV).
The time-averaged spectrum from T0-2.56 s to T0+20.9 s is
adequately fit by a Band function with Epeak = 189 +/- 37 keV,
alpha = -0.8 +/- 0.1, and beta = -2.0 +/- 0.2
(chi squared 369 for 325 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(8.0 +/- 0.8)E-6 erg/cm^2. The 0.256-sec peak photon flux measured
starting from T0+6.15 s in the 8-1000 keV band
is 7.4 +/- 3.0 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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