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GCN Circular 9346

GRB 090502: Fermi GBM detection
2009-05-11T15:52:55Z (15 years ago)
Vandiver Chaplin at UAH/Fermi-GBM <>
V.Chaplin (UAH) reports on behalf of the
Fermi GBM Team:

"At 18:39:34.64 UT on 02 MAY 2009, the Fermi Gamma-ray
Burst Monitor (GBM) triggered and located GRB 090502
(trigger 262982376 / 090502777). The on-ground calculated
location, using the GBM trigger data, is
RA = 267.8, Dec = -20.3 (J2000 degrees, equivalent to
J2000 17h 51m, -20d 18'), with a statistical uncertainty
of 7.4 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 77 degrees.

The GBM light curve shows a multi-peaked burst with a
duration (T90) of about 66.2 s (8-1000 keV). The
time-averaged spectrum from T0-11.6 to T0+62.1 s
is best fit by a power-law with an exponential cut-off,
with alpha = -1.1 +/- 0.3 and E-peak = 63.2 +/- 8.7 keV,
(chi squared 227.86 for 241 d.o.f.)

The fluence (8-1000 keV) in this time interval is
(3.5 +/- 0.9)E-08 erg/cm^2. The 1-second peak photon
flux starting from T0+37.5 is 6.2 +/- 0.9 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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