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GCN Circular 35560

Subject
GRB 240118A: Fermi-LAT detection
Date
2024-01-18T09:58:01Z (3 months ago)
From
Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it>
Via
Web form
E. Bissaldi (Politecnico and INFN Bari), F. Longo (University and INFN Trieste)
and Makoto Arimoto (Kanazawa University) report on behalf of the Fermi-LAT Collaboration:


At 01:48:09.44 on January, 18, 2024 Fermi-LAT detected high-energy emission
from GRB 240118A, which was also detected by Fermi-GBM (trigger 727235294 / 240118075, 
GCN #35558).

The best LAT on-ground location is found to be

RA, Dec = 18.57, 29.79 (J2000)

with an error radius of 0.05 deg (90 % containment, statistical error only).
This was 69 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate
that is spatially and temporally correlated with the trigger with high significance.
The photon flux above 100 MeV in the time interval 0-2000 s
after the GBM trigger time is (7.3 +/- 1.0)E-6 ph/cm2/s.
The estimated photon index above 100 MeV is -1.9 +/- 0.1.
The highest-energy photon is a 41 GeV event, which is observed 
732 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is 
Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it).

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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