[vsnet-grb-info 19686] GRB 170808B: Fermi LAT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21430
SUBJECT: GRB 170808B: Fermi LAT Detection
DATE:    17/08/09 05:59:27 GMT
FROM:    Daniel Kocevski at GSFC  <daniel.kocevski at nasa.gov>

F. Longo (University and INFN, Trieste) and D. Kocevski (NASA MSFC) report on behalf of the Fermi-LAT team:
At 22:27:43.10 UT on August 08, 2017, Fermi-LAT detected high-energy emission from GRB 170808B, which was also detected by Fermi-GBM (Veres and Meegan GCN 21429). 
The best LAT on-ground location is found to be
RA, Dec  145.66, 2.18 deg, J2000
with an error radius of 0.34 deg (90% containment, statistical error only). This was 69 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 detection with high significance.
The highest-energy photon is a 1.62 GeV event which is observed 162 seconds after the GBM trigger.
A Swift ToO has been requested for this burst. <https://confluence.slac.stanford.edu/pages/createpage.action?spaceKey=SCIGRPS&title=A+Swift+ToO+has+been+requested+for+this+burst%3F&linkCreation=true&fromPageId=103583868>
The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo at ts.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.