[vsnet-grb-info 19695] GRB 170810A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21452
SUBJECT: GRB 170810A: Fermi-LAT detection
DATE:    17/08/11 02:24:00 GMT
FROM:    Judith Racusin at GSFC  <judith.racusin at nasa.gov>

J. L. Racusin (NASA/GSFC), E. Burns (NASA/GSFC), D. Kocevski (NASA/MSFC), F. Longo (University 
and INFN, Trieste), J. McEnery (NASA/GSFC), S. Razzaque (Johannesburg), G. Vianello (Stanford), 
report on behalf of the Fermi-LAT team:

Fermi-LAT detected high-energy emission from GRB 170810A, which trigger Fermi-GBM (trigger 
524095306 / 170810918) and Swift-BAT (Gibson et al, GCN 21450) at 22:01:41 on August, 10, 2017.

The best LAT on-ground location is found to be

RA, Dec = 187.5, 3.33 (J2000)

with an error radius of 0.53 deg (90 % containment, statistical error only), which is consistent with the 
Swift BAT, XRT, and UVOT positions (Gibson et al, GCN 21450; Goad et al., GCN 21451), as well as 
MASTER-NET (Rebolo et al, GCN 21449).

This was 60 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally 
correlated with the trigger with high significance.

The highest-energy photon is a 2.3 GeV event which is observed 34 seconds after the GBM trigger.

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.