GCN Circular 20785

E. Bissaldi (Politecnico & INFN Bari), F. Longo (University & INFN Trieste),
E. Moretti (MPI Munich), M. Yassine (LUPM) and Z. Acuner (KTH Stockholm)
report on behalf of the Fermi-LAT team:


At 19:03:00.71 UT on February, 28, 2017, Fermi-LAT detected high-energy emission
from GRB 170228A, which was also detected by Fermi-GBM (trigger 170228794/510001385).

The best LAT on-ground location is found to be

RA, Dec = 239.55, -3.59 (J2000)

with an error radius of 0.3 deg (90 % containment, statistical error only).

This was about 70 deg from the LAT boresight at the time of the trigger.
The burst entered the LAT FoV about 80 s post trigger and exited about 800 s post trigger.
The data from the Fermi-LAT show a significant increase in the event rate that
is spatially correlated with the trigger with high significance.
In total, LAT detected about 20 photons with an energy greater than 100 MeV.
The highest-energy photon is a 5 GeV event, which is observed 130
seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Zeynep Acuner (acuner@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.