TITLE:   GCN CIRCULAR
NUMBER:  21032
SUBJECT: GRB 170424A: Fermi-LAT detection
DATE:    17/04/24 22:00:23 GMT
FROM:    Nicola Omodei at Stanford U.  <nicola.omodei@slac.stanford.edu>

N. Omodei, G.Vianello (Stanford University), report on behalf of the Fermi-LAT team:

At 10:12:30.75 on April, 24, 2017 Fermi-LAT detected high-energy emission from GRB 170424A, which was also detected by Fermi-GBM (trigger 514721555 / 170424425).

The best LAT on-ground location is found to be

RA, Dec = 343.7, -45.12 (J2000)

with an error radius of 0.45 deg (90 % containment, statistical error only). 

This was 57 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 1 GeV event which is observed 56 seconds after the GBM trigger. 

The GRB was also detected using LAT Low Energy (LLE) data selection, with a significance of 6 sigma. 

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Nicola Omodei (nicola.omodei@stanford.edu).

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.