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GCN Circular 31125

GRB 211118A: Fermi GBM detection
2021-11-25T15:18:49Z (3 years ago)
Joe Mangan at UCD <>
J.Mangan (UCD), R. Dunwoody (UCD) and C.Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 23:38:14.587 UT on 18 November 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 211118A (trigger 658971499 / 211118985).
which was also detected by the Swift/BAT-GUANO (Raman et al. 2021, GCN 31096).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 33.7, Dec = 71.1(J2000 degrees, equivalent to J2000 02h 15m, 71d 03'),
with a statistical uncertainty of 2.7 degrees (radius, 1-sigma
containment, statistical only;
there is additionally a systematic error which we have characterized
as a core-plus-tail model,
with 90% of GRBs having a 3.7 deg error and a small tail suffering
a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS,
216, 32] )

The angle from the Fermi LAT boresight at the GBM trigger time is 127 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 7.2 s (50-300 keV).
The time-averaged spectrum from T0-0.002 s to T0+7.776 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.21 +/- 0.07 and
the cutoff energy, parameterized as Epeak, is 2176 +/- 865 keV

The event fluence (10-1000 keV) in this time interval is
(3.975 +/- 0.272)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band
is 7.1 +/- 0.5 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB

For Fermi GBM data and info, please visit the official Fermi GBM
Support Page:"
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