{
  "createdOn": 1737541654484,
  "bibcode": "2025GCN.39010....1H",
  "subject": "GRB 250121A: Fermi-LAT detection",
  "body": "A. Holzmann Airasca (UniTrento and INFN Bari), D. Depalo (Politecnico and INFN Bari), E. Bissaldi (Politecnico and INFN Bari), R. Gupta (NASA GSFC), C. Bartolini (UniTrento and INFN Bari), S. Lopez (CNRS / IN2P3) on behalf of the Fermi-LAT Collaboration:\n\nOn January 21, 2025, Fermi-LAT detected high-energy emission from GRB 250121A, which was also detected by Fermi-GBM (trigger 759195370 / 250121983, GCN 39006).\n\nThe best LAT on-ground location is found to be:\nRA, Dec = 225.14, -34.37 (J2000)\n\nwith an error radius of 0.24 deg (90 % containment, statistical error only). This was 15 deg from the LAT boresight at the time of the GBM trigger (T0 = 23:36:05.78 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 - 500 s after the GBM trigger is (2.5 ± 1.2) E-6 ph/cm2/s. The estimated photon index above 100 MeV is 1.7 ± 0.3. The highest-energy photon is a 2.6 GeV event which is observed ~ 15 seconds after the GBM trigger.\n\nThe Fermi-LAT point of contact for this burst is Aldana Holzmann Airasca (aldana.holzmannairasca@ba.infn.it).\n\nThe 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.",
  "submitter": "A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>",
  "submittedHow": "web",
  "circularId": 39010,
  "eventId": "GRB 250121A",
  "format": "text/plain"
}