GCN Circular 35342

D. Kocevski (NASA/MSFC), N. Di Lalla (Stanford University), M. Arimoto
(Kanazawa University), and T. Khalil (Johannesburg University) report
on behalf of the Fermi-LAT Collaboration:

On December 14, 2023 Fermi-LAT detected high-energy emission from GRB
231214A, which was also detected by Fermi-GBM (trigger
724278269.684604 / 231214850, GCN 35334
Not found
 
 
), Swift-BAT and Swift-XRT (GCN
35335
Not found
 
 
, 35341
Not found
 
 
).

The best LAT on-ground location is found to be
RA, Dec = 306.1, -72.4 (degrees, J2000)
with an error radius of 0.2 deg (90% containment, statistical error
only). This was 51 deg from the LAT boresight at the time of the GBM
trigger: T0 = 20:24:24.69 UT.

The data from the Fermi-LAT show a significant increase in the event
rate after the GBM trigger that is spatially correlated with the GBM
emission with high significance. The photon flux above 100 MeV in the
time interval 0-3000 s after the GBM trigger is (3.9 +/- 0.8)E-6
ph/cm2/s.
The estimated photon index above 100 MeV is -1.9 +/- 0.2. The
highest-energy photon is a 2.9 GeV event which is observed 414 seconds
after the GBM trigger.
The Fermi-LAT point of contact for this burst is Tamador Khalil
(tamtam2030@gmail.com)

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.