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GCN Circular 32283

GRB 220627A: Fermi-LAT detection
2022-06-28T07:00:40Z (2 years ago)
Magnus Axelsson at Stockholm U. <>
N. Di Lalla (Stanford Univ.), M. Axelsson (KTH & Stockholm Univ.), M. Arimoto (Kanazawa Univ.), N. Omodei (Stanford Univ.) and M. Crnogor�evi� (Univ. of Maryland & NASA/GSFC) report on behalf of the Fermi-LAT team:

On June 27, 2022, Fermi-LAT detected high-energy emission from GRB 220627A, which was also detected by Fermi-GBM (trigger 678057665 / 220627890, GCN 32278).

The best LAT on-ground location is found to be

RA, Dec = 201.2, -32.5 (degrees, J2000)

with an error radius of 0.2 deg (90 % containment, statistical error only). This was 27 deg from the LAT boresight at the time of the GBM trigger:

T0 = 21:21:00.9 UT.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The 100 MeV - 1 GeV photon flux in the time interval 0-600 s after the GBM trigger is (1.8 +/- 0.3)E-05 ph/cm2/s, and the photon flux above 1 GeV is (1.3 +/- 0.4)E-06 ph/cm2/s. The estimated photon index above 100 MeV is -2.2 +/- 0.15. The highest-energy photon is a 15.7 GeV event which is observed 176 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Milena Crnogor�evi� (<>).

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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