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GCN Circular 9413

Subject
GRB 090516B: Fermi GBM detection
Date
2009-05-20T17:04:52Z (15 years ago)
From
Sheila McBreen at MPE <smcbreen@mpe.mpg.de>
Sheila McBreen (UCD/MPE)
reports on behalf of the Fermi GBM Team:

"At 03:17:20.17 UT on 16 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090516B (trigger 264136642 / 090516137).

The on-ground calculated location, using the GBM trigger
data, is RA = 122.2, DEC = -71.62 (J2000 degrees,
equivalent to 08 h 09 m, -71 d 37 '), with an uncertainty
of 2.6 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 45 degrees.

The GBM light curve consists of several overlapping
peaks from the trigger to about 140 s and possible
weak emission out to about 350 s.

The time-averaged spectrum from T0 s to T0+138 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.01 (+/-0.06) and
the cutoff energy, parameterized as Epeak, is
327.0 (+/-58.7) keV (chi squared 419 for 359 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(3.0 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+80 s in the 8-1000 keV band
is 4.0 +/- 0.2 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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