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GCN Circular 9428

Subject
GRB 090520C: Fermi GBM detection
Date
2009-05-28T13:32:02Z (15 years ago)
From
Narayana Bhat at U Alabama/Huntsville/GBM <Narayana.Bhat@nasa.gov>
P. N. Bhat (UAH)
report on behalf of the Fermi GBM Team:

"At 20:23:19.31 UT on 20 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090520C (trigger 264543801 / 090520850).

The on-ground calculated location, using the GBM trigger
data, is RA = 111.2, DEC = -19.7 (J2000 degrees,
equivalent to 07 h 24.8 m, -19 d 42'), with an uncertainty
of 1.2 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 71 degrees.

The GBM light curve consists of single peak
with a duration (T90) of about 4.9 s (10-1000 keV).
The time-averaged spectrum from T0-0.512 s to T0+3.968 s is
adequately fit by a Band function with Epeak = 204.2 +/- 27.9 keV,
alpha = -0.73 +/- 0.09, and beta = -1.96 +/- 0.10

(chi squared 400.9for 362 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(3.54 +/- 0.25)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.872 s in the 8-1000 keV band
is 4.47 +/- 0.32 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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