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GCN Circular 10018

GRB 091010: Fermi GBM observation
2009-10-12T15:05:12Z (15 years ago)
David Gruber at MPE <>
A. von Kienlin, E. Bissaldi and D. Gruber (all MPE)
report on behalf of the Fermi GBM Team:

"At 02:43:09.32 UT on 10 October 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 091010 (trigger 276835391 / 091010113),
which was also detected by SuperAGILE (Donnarumma et al., GCN 10004).
The GBM on-ground location is consistent with the Swift-XRT position
(Margutti et al. 2009, GCN 10006 and Evans et al. 2009, GCN 10012).

The angle from the Fermi LAT boresight is 55.7 degrees.
Moreover, this burst was bright enough to result in
a Fermi spacecraft repointing maneuver.

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

The GBM light curve consists of multiple peaks
with a duration (T90) of about 8.1 +/- 0.5 s (8-1000 keV).
The time-averaged spectrum from T0-0.128 s to T0+8.064 s is
best fit by a power law function with an exponential
high energy cutoff. The power law index is -1.11 +/- 0.03 and
the cutoff energy, parameterized as Epeak, is 150 (+6/-5) keV
(C-stat 446 for 359 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.09 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.9 s in the 8-1000 keV band
is 40.9 +/- 0.5 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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