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GCN Circular 9983

GRB 091003A: Fermi GBM detection
2009-10-03T11:42:08Z (15 years ago)
Arne Rau at MPE <>
Arne Rau (MPE) reports on behalf of the Fermi GBM Team:

"At 04:35:45.58 UT on 03 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 091003A (trigger 276237347 / 091003191).

The on-ground calculated location, using the GBM trigger
data, is RA = 251.1, DEC = 37.2 (J2000 degrees,
equivalent to 16h 44m, 37d 12'), with an uncertainty
of 1.0 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 13 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of multiple peaks
with a duration (T90) of about 21.1 +/- 0.5s (8-1000 keV).
The time-averaged spectrum from T0-0.384s to T0+23.168s is
best fit by a Band function with Epeak = 486.2 +/- 23.6 keV,
alpha = -1.13 +/- 0.01, and beta = -2.64 +/- 0.24
(chi squared 851 for 611 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(3.76 +/- 0.04)E-05 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+18.048 s in the 8-1000 keV band
is 31.8 +/- 0.4 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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