TITLE:   GCN CIRCULAR
NUMBER:  20826
SUBJECT: GRB 170306B: Fermi-LAT detection
DATE:    17/03/06 18:58:37 GMT
FROM:    Nicola Omodei at Stanford U.  <nicola.omodei@slac.stanford.edu>

N. Omodei (Stanford U.), G, Vianello (Stanford U.), D. Tak(U. of 
Maryland) and F. Longo (University and INFN Trieste) report on behalf of 
the Fermi-LAT team:
At 14:07:22.27 on March 06, 2017, Fermi-LAT detected high-energy 
emission from GRB 170306B, which was also detected by Fermi-GBM (trigger 
510502047).
The best LAT on-ground location is found to be RA, Dec 154.62, 51.59 
(degrees, J2000) with an error radius of 0.61 deg (90% containment, 
statistical error only).
This was 55 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 within 4.3 degree of the GBM location after the GBM trigger that is 
temporally correlated with the GBM emission with high significance.
More than 10 photons above 100 MeV are observed within 300 seconds.
The highest-energy photon is a 500 MeV event which is observed 46 
seconds after the GBM trigger.
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.