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GCN Circular 28828

GRB 201104A: Fermi-LAT detection
2020-11-04T20:30:07Z (4 years ago)
Masanori Ohno at Hiroshima University <>
M. Ohno (Hiroshima U./Eotvos U.), N. Omodei (Stanford University), F. Longo
(University & INFN Trieste) and M. Axelsson (KTH & Stockholm Univ.)
report on behalf of the Fermi-LAT Collaboration:

On November 4, 2020, Fermi-LAT detected high-energy emission from
GRB 201104A, which was also detected by Fermi-GBM (trigger
626140861/201104001) (Fermi-GBM team; GCN Circ. 28823).

The best LAT on-ground location is found to be

RA, Dec = 81.4, -71.1 (degrees, J2000)

with an error radius of 0.24 deg (90% containment, statistical error only).
This was 6.7 deg from the LAT boresight at the time of the GBM trigger:
T0 =  00:00:56 UT.

The source quickly went out from the LAT FoV but the data from the
Fermi-LAT show a significant increase
in the event rate after the GBM trigger that is spatially and temporally
correlated with the
GBM emission with high significance.
The photon flux above 100 MeV in the time interval 0-100 s after the
GBM trigger is (2.6+/-0.4)e-4 ph/cm2/s.

The estimated photon index above 100 MeV is -2.5 +/-  0.2.

The highest-energy photon is a 3.7 GeV event which is observed  16 seconds
after the GBM trigger.

A Swift ToO has been requested for this burst

The Fermi-LAT point of contact for this burst is
Masanori Ohno (

The Fermi-LAT is a pair conversion telescope designed to cover
the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration between
NASA and DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.

[GCN OPS NOTE(06Nov20): Due to the uncertainty of the arrival time with respect
to the downtime window (15 hours) of the GCN Circulars processing system, 
the error in the date-time in the header of this Circular can be off anywhere from 0-15 hours.]
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