TITLE:   GCN CIRCULAR
NUMBER:  22961
SUBJECT: GRB 180718B: Fermi-LAT detection
DATE:    18/07/19 04:24:04 GMT
FROM:    Judith Racusin at GSFC  <judith.racusin@nasa.gov>

M. Crnogorcevic (NASA/GSFC/UMD), G. Vianello (Stanford), J. L. Racusin (NASA/GSFC), 
M. Axelsson (KTH and Stockholm University), and E. Bissaldi (Politecnico and INFN Bari), report 
on behalf of the Fermi-LAT team:

At 18:18:24.46 UT on July, 18, 2018 Fermi-LAT detected high-energy emission from GRB 180718B, 
which was also detected by Fermi-GBM (trigger 553630709 / 180718763). 

The best LAT on-ground location is found to be
RA, Dec = 44.68, -31.5 (J2000)

with an error radius of 0.65 deg (90% containment, statistical error only). 

This was 50 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 highest-energy photon is a 300 MeV event which is observed 17 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it).

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.