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GCN Circular 31350

GRB 220101A: Fermi-LAT detection
2022-01-01T14:08:57Z (2 years ago)
Lorenzo Scotton at CNRS/IN2P3/LUPM <>
M. Arimoto (Kanazawa Univ.), L. Scotton (CNRS/IN2P3/LUPM) and F. Longo 
(University and INFN, Trieste)
report on behalf of the Fermi-LAT Collaboration:

On January 1st, 2022, Fermi-LAT detected high-energy emission from
GRB 220101A, which was also detected by Swift (trigger 1091527, 
Tohuvavohu et al. GCN Circ. 31347)

The best LAT on-ground location is found to be

RA, Dec = 1.52, 31.75 (degrees, J2000)

with an error radius of 0.46 deg (90% containment, statistical error only).
This was 18 deg from the LAT boresight at the time of the Swift trigger:

T0 = ��05:10:11.5 UT.

The data from the Fermi-LAT show a significant increase
in the event rate after the Swift trigger that is spatially correlated 
with the
Swift emission (0.14 degrees from the Swift-XRT location) with high 
The photon flux above 100 MeV in the time interval 0-600s after the
Swift trigger is 2.5E-5 +/- 5E-6 ph/cm2/s.

The estimated photon index above 100 MeV is -2.46 +/- 0.25.

The Fermi-LAT point of contact for this burst is
Lorenzo Scotton (lorenzo.scotton AT

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.
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