[vsnet-grb-info 19309] GRB 170409A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21004
SUBJECT: GRB 170409A: Fermi-LAT detection
DATE:    17/04/09 15:48:54 GMT
FROM:    Judith Racusin at GSFC  <judith.racusin at nasa.gov>

F. Longo (University and INFN, Trieste), J. L. Racusin (NASA/GSFC), and 
D. Kocesvki (NASA/MSFC)report on behalf of the Fermi-LAT team:

At 02:41:59.49 on April 9, 2017, Fermi-LAT detected high-energy emission 
from GRB 170904A, which was also detected by Fermi-GBM (trigger 
513398525/170409112). 

The best LAT on-ground location is found to be:

RA, Dec = 347.53, -7.16 (degrees, J2000)

with an error radius of 0.15 deg (90% containment, statistical error only). This 
was 82 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 consistent with the GBM emission. More than 14 
photons above 100 MeV and 2 photons above 1 GeV are observed within 1000 
seconds.  The highest-energy photon is a 10 GeV event which is observed 442 
seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

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.