GCN Circular 19444

M. Axelsson (KTH Stockholm), E. Bissaldi (Politecnico and INFN Bari), J. McEnery
(NASA/GSFC), F. Dirirsa (Univ. of Johannesburg) and J.M. Burgess (KTH Stockholm)
report on behalf of the Fermi-LAT team:

At UT 09:13:58.03 on May 21, 2016, Fermi-LAT detected high-energy emission
from GRB 160521B, which was also detected by Fermi-GBM
(trigger 485514841/160521385).

The best LAT on-ground location is found to be

RA, Dec = 148.17, 79.01 (degrees, J2000)

with an error radius of 0.17 deg (90% containment, statistical error only).
This was 47 deg from the LAT boresight at the time of the trigger and triggered
an autonomous repoint of the spacecraft.

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.
More than 10 photons above 100 MeV are observed within 3000 seconds, with
the highest-energy photon being a 12 GeV event observed 420 seconds after
the GBM trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is Magnus Axelsson (magaxe@kth.se<mailto:magaxe@kth.se>).

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.