GCN Circular 41161
Subject
GRB 250725A: Fermi-LAT detection
Event
Date
2025-07-25T10:33:39Z (a month ago)
From
A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>
Via
Web form
A. Holzmann Airasca (UniTrento and INFN Bari), F. Longo (University and INFN, Trieste), D. Depalo (Politecnico and INFN Bari) and R. Gupta (NASA/GSFC) report on behalf of the Fermi-LAT Collaboration:
On July 25, 2025, Fermi-LAT detected high-energy emission from GRB 250725A, which was also detected by Fermi-GBM (trigger 775101099 / 250725077, GCN 41150), Swift-BAT (GCN 41152), Swift-XRT (GCN 41153), MASTER-OAFA (GCN 41157), SVOM/VT (GCN 41158), BOOTES-7 (GCN 41159) and VLT/FORS2 (GCN 41160).
The best LAT on-ground location is found to be:
RA, Dec = 34.6, -83.2 (J2000)
with an error radius of 1.1 deg (90 % containment, statistical error only).
This was 24 deg from the LAT boresight at the time of the GBM trigger (T0 = 01:51:34.81 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 0 - 90 s after the GBM trigger is (1.26 ± 0.50) E-5 ph/cm2/s. The estimated photon index above 100 MeV is -2.07 ± 0.40.
The highest-energy photon is a 1 GeV event which is observed ~ 15 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@ts.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.