GCN Circular 36901
Subject
GRB 240718A: Fermi-LAT Detection
Date
2024-07-18T15:51:08Z (4 months ago)
From
Davide Depalo at Politecnico and INFN Bari <davide.depalo@ba.infn.it>
Via
Web form
D. Depalo (Politecnico & INFN Bari), E. Bissaldi (Politecnico & INFN Bari), R. Gupta (NASA/GSFC), and A. Holzmann (DF, University of Buenos Aires, Argentina) report on behalf of the Fermi-LAT Collaboration:
At 06:29:00 UT on July, 18, 2024 Fermi-LAT detected high-energy emission from GRB 240718A which was also detected by Fermi-GBM (trigger 742976945 / 240718270, GCN 36898) and SVOM/GRM (GCN 36900).
The best LAT on-ground location is found to be
RA, Dec = 252.78, -25.11 (J2000)
with an error radius of 0.23 deg (90 % containment, statistical error only).
This was 52 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 0-400 s after the GBM trigger is (1.25 +/- 0.43) E-5 ph/cm2/s. The estimated photon index above 100 MeV is - 2.2 +/- 0.3.
The highest-energy photon is a 2.7 GeV event which is observed about 17 seconds after the GBM trigger.
A Swift ToO has been requested.
The Fermi-LAT point of contact for this burst is Davide Depalo (d.depalo2@phd.poliba.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.