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GCN Circular 27797

Subject
GRB 200524A: Fermi-LAT detection
Date
2020-05-24T14:49:12Z (4 years ago)
From
Masanori Ohno at Hiroshima University <ohno@astro.hiroshima-u.ac.jp>
F. Fana Dirirsa (Univ. of Johannesburg), M. Axelsson (KTH & Stockholm
Univ.), M. Ohno (Hiroshima Univ.), F. Piron (CNRS/IN2P3/LUPM) and F. Longo
(University and INFN, Trieste) report on behalf of the Fermi-LAT
Collaboration:

On May 24, 2020, Fermi-LAT detected high-energy emission from
GRB 200524A, which was also detected by Fermi-GBM (trigger 611989445).

At the time of the trigger (T0 = 05:04:00.36 UT) Fermi-LAT was passing
through the SAA, and observations started at roughly
T0+110 seconds. The GRB is detected at high energy (>100 MeV) by Fermi-LAT
at a location of:

RA, Dec = 212.8, 61.0 (degrees, J2000) with an error radius of 0.2 deg (90%
containment, statistical error only).

This was ~25 deg from the LAT boresight when observations started
(T0+110s), and is ~3 deg from the GBM final ground position.

The photon flux above 100 MeV in the time interval 110-900 s after the GBM
trigger is 2.2e-06 +/- 0.8e-06 ph/cm2/s. The estimated photon index above
100 MeV is -1.7 +/ - 0.2. The highest-energy photon is a 9.2 GeV event
which is observed 748 seconds after the GBM trigger. After ~T0+900s, the
GRB location moved outside the LAT FoV.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is
Feraol Fana Dirirsa (fdirirsa@uj.ac.za ).

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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