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GCN Circular 33650

GRB 230402A: Fermi-LAT detection
2023-04-18T20:49:24Z (a year ago)
N. Di Lalla at Stanford University <>
F. Longo (University and INFN, Trieste), E. Bissaldi (Politecnico and INFN, Bari), N. Di Lalla (Stanford Univ.) and N. Omodei (Stanford Univ.) report on behalf of the Fermi-LAT team:

At 07:32:35.96 on April, 02, 2023 Fermi-LAT detected high-energy emission from GRB 230402A, which was also detected by Fermi-GBM (trigger 702113560 / 230402314, GCN 33553), AGILE (GCN 33555), AstroSat (GCN 33562) and CALET (GCN 33563)

The best LAT on-ground location is found to be

RA, Dec = 96.4, -8.9 (J2000)

with an error radius of 0.4 deg (90 % containment, statistical error only).
This was 24 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 100 MeV - 1 GeV photon flux in the time interval 0-300 s after the GBM trigger is (7 ± 2)E-06 ph/cm2/s. The estimated photon index above 100 MeV is -2.6 ± 0.5.

The highest-energy photon is a 1.2 GeV event which is observed 14 seconds after the GBM trigger.

The Fermi-LAT point of contact for this burst is Francesco Longo (

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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