GCN Circular 32831

GRB 221023A: Fermi-LAT detection

Pillera R. (Politecnico and INFN Bari), Cutini S. (INFN Perugia), Maheso 
D. (Johannesburg Univ.),
Cheung C. C. (Naval Research Laboratory), Bissaldi E. (Politecnico and 
INFN Bari),
Di Lalla N. (Stanford Univ.) and Khalil T. (Johannesburg Univ.) report 
on behalf of the Fermi-LAT team:

At 20:41:34.92 on October, 23, 2022 Fermi-LAT detected high-energy 
emission
from GRB 221023A, which was reported by AGILE (Ursi et al. GCN 32825
Not found
 
 
) 
and GBM (GBM team 32826).


The best LAT on-ground location is found to be

RA, Dec =  230.30, 15.01 (J2000)

with an error radius of 0.04 deg (90 % containment, statistical error 
only).
This was 48 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 0-1600 s after
the GBM trigger is (7.0 +/- 0.3)E-05 ph/cm2/s.
The estimated photon index above 100 MeV is -2.25 +/- 0.05.
The highest-energy photon is a 17 GeV event with 99% probability
which is observed 576 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.