[vsnet-grb-info 28272] GRB 210704A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30375
SUBJECT: GRB 210704A: Fermi-LAT detection
DATE:    21/07/05 11:19:51 GMT
FROM:    Francesco Longo at U of Trieste,INFN Trieste  <franzlongo1969 at gmail.com>

A. Berretta (University & INFN Perugia), F. Longo (University and
INFN, Trieste),
M. Axelsson (KTH & Stockholm Univ.), E. Bissaldi (Politecnico and INFN, Bari),
F. Piron (CNRS/IN2P3/LUPM) and M. Arimoto (Kanazawa Univ.)
report on behalf of the Fermi-LAT Collaboration:

On July 4th, 2021, Fermi-LAT detected high-energy emission from GRB 210704A
which was also detected by Fermi-GBM (trigger 647120009/210704815) and
by AGILE/MCAL (GCN 30372).

The best LAT on-ground location is found to be
RA, Dec = 159.08, 57.31 (degrees, J2000)
with an error radius of 0.11 deg (90% containment, statistical error only).
This was 63 deg from the LAT boresight at the time of the GBM trigger:
T0 = 19:33:24.59 UT.

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

The photon flux above 100 MeV in the time interval 0-10s after the GBM trigger
is (1.60 +/- 0.31) E-03 ph/cm2/s.
The estimated photon index above 100 MeV is -1.74 +/- 0.13.
The highest-energy photon is a 16 GeV event which is observed 1.5 seconds
after the GBM trigger.

The Fermi-LAT point of contact for this burst is Alessandra Berretta
(alessandra.berretta at pg.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.