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GCN Circular 9558

Subject
GRB 090621C: Fermi GBM detection
Date
2009-06-22T19:42:15Z (15 years ago)
From
Arne Rau at MPE <arau@mpe.mpg.de>
Arne Rau (MPE) reports on behalf of the Fermi GBM Team:

"At 10:00:52.10 UT on 21 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090621C (trigger 267271254 / 090621417).

The on-ground calculated location, using the GBM trigger
data, is RA = 257.5 deg, DEC = -28.5 deg (J2000 degrees,
equivalent to 17 h 10 m, -28 d 28 '), with an uncertainty
of 3.3 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 52 degrees.

The GBM light curve consists of multiple short peaks
with a duration (T90) of about 59.9 s (8-1000 keV).
The time-averaged spectrum from T0-3.072 s to T0+28.672 s is
well fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.4 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 148 +/- 34 keV
(chi squared 444 for 461 d.o.f.).

The event fluence (8-1000 keV) in the above mentioned time interval is
(1.8 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+4.096 s in the 8-1000 keV band
is 2.29 +/- 0.06 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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