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GCN Circular 14971

Subject
GRB 130702A / Fermi394416326 : Fermi-LAT detection of a burst
Date
2013-07-03T17:34:28Z (11 years ago)
From
Giacomo Vianello at SLAC <giacomov@slac.stanford.edu>
T. Cheung (NRL), G.Vianello (Stanford), S. Zhu (NASA/GSFC), J. Racusin
(NASA/GSFC), V. Connaughton (UAH) and B. Carpenter (NASA/GSFC) report
on behalf of the Fermi-LAT team:

At 00:05:23.079 UTC on July 02, 2013, Fermi GBM triggered on GRB
130702A / Fermi394416326 (trigger 394416326). The LAT detected high
energy emission from this GRB, which was also detected in the optical
band by iPTF (Singer et al., GCN 14967) and confirmed by FTN (Guidorzi
et al., GCN 14968).

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

RA, DEC = 216.4, 15.8 (J2000), with an error radius of 0.5 deg (90%
containment, statistical error only)

This position is 4 deg from the best GBM position (RA, Dec = 218.81,
+12.25 with a 4 deg radius), and 0.8 deg from the position of the
optical afterglow. A preliminary IPN triangulation of the burst using
GBM and Konus-Wind data gives an annulus with center RA, DEC =
260.8992, -20.7746 (J2000) of radius 50.85 degrees and a width of
(-32.73,+18.42) deg (3 sigma). The center of this annulus is 6.05 deg
(0.99 sigma) from the LAT location (Private Communication, with
possible IPN refinements using data from distant spacecraft).

The best LAT localization for the source was ~75 deg from the LAT
boresight at the time of the trigger, i.e., outside the nominal field
of view of the LAT (~65 deg), but it entered the FOV at T0+250 s to
exit again at T0 + 2200 s.

The data from the Fermi LAT in such time interval show a significant
increase in the event rate within 10 degree of the source location,
with a significance of more than 5 sigmas. This analysis has been
carried out with the P7SOURCE_V6 class. More than 5 photons above 100
MeV are observed within 2200 seconds. The highest energy photon is a
1.5 GeV event which is observed 260 seconds after the GBM trigger.

The Fermi LAT point of contact for this burst is Giacomo Vianello
(giacomov@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.
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