TITLE: GCN CIRCULAR NUMBER: 40611 SUBJECT: GRB 250602A: Fermi-LAT detection DATE: 25/06/02 20:13:59 GMT FROM: Rahul Gupta at NASA GSFC rahul.gupta@nasa.gov
A. Holzmann Airasca (UniTrento and INFN Bari), S. Lopez (CNRS / IN2P3), R. Gupta (NASA GSFC), F. Longo (University and INFN, Trieste), N. Di Lalla (Stanford Univ.), and J. Racusin (NASA GSFC) report on behalf of the Fermi-LAT Collaboration:
On June 02, 2025, Fermi-LAT detected high-energy emission from GRB 250602A, which was also detected by Fermi-GBM (trigger 770526276 / 250602128, GCN 40602).
The best LAT on-ground location is found to be:
RA, Dec = 111.9, 56.9 (J2000)
with an error radius of 0.4 deg (90 % containment, statistical error only). This was 111 deg from the LAT boresight at the time of the GBM trigger (T0 = 03:04:31.31 UT).
The data from the Fermi-LAT shows a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 3000 - 8000 s after the GBM trigger is (8.2 ± 3.2) E-7 ph/cm2/s. The estimated photon index above 100 MeV is -2.17 ± 0.33.
The highest-energy photon is a 1.6 GeV event which is observed ~ 4800 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Rahul Gupta (rahul.gupta@nasa.gov).
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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