GCN Circular 32862
Subject
GRB 221027A: Fermi-LAT detection
Date
2022-10-27T10:28:51Z (2 years ago)
From
Makoto Arimoto at Tokyo Inst of Tech <arimoto@hp.phys.titech.ac.jp>
Arimoto M. (Kanazawa University), Bissaldi E. (Politecnico and INFN Bari),
Longo F. (University and INFN Trieste), Scotton L. (CNRS/IN2P3/LUPM)
and Maheso D. (Johannesburg Univ.) report on behalf of the Fermi-LAT
team:
On October, 27, 2022 Fermi-LAT detected high-energy emission from GRB 221027A,
which was also detected by Fermi-GBM (trigger 221027173 / 688536579,
GCN 32861) at 04:09:34.35 UT .
The best LAT on-ground location is found to be
RA, Dec = 185.3, -5.7 (J2000)
with an error radius of 0.4 deg (90 % containment, statistical error only).
This was 51 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 0-500 s after
the GBM trigger is (9.1 +/- 2.6)E-06 ph/cm2/s.
The estimated integrated photon index above 100 MeV is -2.2 +/- 0.3.
The highest-energy photon is a 1.1 GeV event with 96% probability
which is observed 26 seconds after the GBM trigger.
A Swift ToO has been requested for this burst.
The Fermi-LAT point of contact for this burst is
Dimakatso Jeannett Maheso (d.j.maheso@gmail.com).
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.