TITLE: GCN CIRCULAR NUMBER: 38963 SUBJECT: GRB 250116A: Fermi-LAT detection DATE: 25/01/16 20:58:26 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it> A. Holzmann Airasca (UniTrento and INFN Bari), S. Lopez (CNRS / IN2P3), N. Di Lalla (Stanford University), T. Khalil (Johannesburg Univ) report on behalf of the Fermi-LAT Collaboration: On January 16, 2025, Fermi-LAT detected high-energy emission from GRB 250116A, which was also detected by Fermi-GBM (trigger 758723644/ 250116524, GCN 38962). The best LAT on-ground location is found to be: RA, Dec = 266.64, -19.36 (J2000) with an error radius of 0.13 deg (90 % containment, statistical error only). This was 53 deg from the LAT boresight at the time of the GBM trigger (T0 = 12:33:59.53 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 - 1500 s after the GBM trigger is (4.0 ± 0.4) E-5 ph/cm2/s. The estimated photon index above 100 MeV is 2.3 ± 0.1. The highest-energy photon is a 3.9 GeV event which is observed 59 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Chiara Bartolini (Chiara.Bartolini@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. View this GCN Circular online at https://gcn.nasa.gov/circulars/38963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...