[vsnet-grb-info 19411] GRB 170522A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21127
SUBJECT: GRB 170522A: Fermi-LAT detection
DATE:    17/05/23 01:46:11 GMT
FROM:    Judith Racusin at GSFC  <judith.racusin at nasa.gov>

M. Arimoto (Waseda University) and J. L. Racusin (NASA/GSFC) report on behalf 
of the Fermi-LAT team:

At 15:45:35.28 on May, 22, 2017 Fermi-LAT detected high-energy emission from GRB 
170522A, which was also detected by Fermi-GBM (trigger 517160740 / 170522657, 
Stanbro et al., GCN 21126). 

The best LAT on-ground location is found to be
RA, Dec = 139.34, 25.67 (J2000)
with an error radius of 0.19 deg (90 % containment, statistical error only). 

This was 50 deg from the LAT boresight at the time of the trigger and triggered an 
autonomous repoint of the spacecraft. The data from the Fermi-LAT show a significant 
increase in the event rate that is spatially and temporally correlated with the GBM trigger with 
high significance.  The highest-energy photon is a 3.7 GeV event which is observed 8 
seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Judith Racusin (judith.racusin at nasa.gov).

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.