GCN Circular 16678

Elena Moretti (MPI Munich), Makoto Arimoto (Tokyo Tech),
Elisabetta Bissaldi (University & INFN Trieste), Sylvain Guiriec
(GSFC/CRESST/UMD) and Giacomo Vianello (Stanford University)
report on behalf of the Fermi-LAT team:


At UT 18:46:10.09 on August 10th, 2014, Fermi-LAT detected
high-energy emission from GRB 140810A, which was also
detected by Fermi-GBM (trigger 140810782/429389173).

The best LAT on-ground location is found to be

(RA, Dec) = 119.04, 27.55 (deg, J2000)

with an approximate error radius of 0.12 deg (90% containment,
statistical error only). The error circle is slightly asymmetric,
the Test Statistic localisation map (with 68% and 90% contours)
can be found here: http://fermigrb.stanford.edu/140810782.jpg.
The location could be updated later as more data become available
(at the moment of writing we can analyse up to 2000 s after the trigger).
The burst was 123 deg from the LAT boresight at the time of
the trigger and the high fluence detected by GBM caused the
GBM flight software to initiate a Fermi autonomous re-point
that placed the source in the LAT FoV about 330 s after the trigger.

The data from the Fermi-LAT show a significant increase
in the event rate that is spatially correlated
with the GBM emission with high significance.
More than 20 photons above 100 MeV and 3 photons
above 1 GeV are observed.
The highest-energy photon is a 16  GeV event,
which is observed about 1500 s after the GBM trigger.

A Swift ToO has been requested for this burst, but the burst can not
be observed due to Sun constrains.

The Fermi-LAT point of contact for this burst
is Elena Moretti (moretti@mpp.mpg.de)


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.