Skip to main content
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 20155

GRB 161109A: Fermi-LAT detection
2016-11-09T14:56:49Z (8 years ago)
Elisabetta Bissaldi at U.Innsbruk/IAPP <>
R. Desiante (INFN Torino), E. Bissaldi (Politecnico & INFN Bari),
F. Longo (University & INFN Trieste), M. Negro (University and INFN Torino),
and J. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team:

At 06:18:45.66 UT on November 09, 2016, Fermi-LAT detected
high-energy emission from GRB 161109A,
which was also detected by Fermi-GBM (trigger 500365129).
The best LAT on-ground location is found to be

RA, Dec: 157.86, 61.80 (degrees, J2000)

with an error radius of 0.26 deg (90% containment, statistical error only).
This was 75 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 GBM emission with high significance.
More than 60 photons above 100 MeV and about 4 photons
above 1 GeV are observed between T0+400 s and T0+1800 s.
The highest-energy photon is a 3.5 GeV event which is
observed 600 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is
Francesco Longo (

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.
Looking for U.S. government information and services? Visit