[vsnet-grb-info 20882] GRB 180720B : Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22980
SUBJECT: GRB 180720B : Fermi-LAT detection
DATE:    18/07/20 22:28:56 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi at ba.infn.it>

E. Bissaldi (Politecnico & INFN Bari) and J. L. Racusin (NASA/GSFC)
report on behalf of the Fermi-LAT team:


"At 14:21:44.55 UT on July 20, 2018, Fermi-LAT detected
high-energy emission from GRB 180720B, which was also
detected by Swift (Siegel et al. 2018, GCN 22973)
and by Fermi-GBM (trigger 553789304 / 180720598).

The best LAT on-ground location is found to be

RA, Dec = 0.58, -2.95 (J2000)

with an error radius of 0.11 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 very high significance.
The highest-energy photon is a 5 GeV event which is
observed 137 seconds after the GBM trigger.
Given that GRB 180720B is detected by both Swift and Fermi,
and it is very bright in the LAT, we encourage follow-up observations.

The Fermi-LAT point of contact for this burst is
Elisabetta Bissaldi (elisabetta.bissaldi at 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."