[vsnet-grb-info 28167] GRB 210619B: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30270
SUBJECT: GRB 210619B: Fermi-LAT detection
DATE:    21/06/20 10:23:35 GMT
FROM:    Roberta Pillera at Politecnico and INFN Bari  <roberta.pillera at ba.infn.it>

M. Axelsson (KTH & Stockholm Univ.), R. Pillera (Politecnico and INFN 
Bari) and
F. Longo (University and INFN Trieste.) report on behalf of the 
Fermi-LAT Collaboration:

Fermi-LAT has detected high-energy emission from GRB 210619B, which was 
also detected
by Swift (GCN 30261), Global MASTER-net (GCN 30262), Ondrejov D50 (GCN 
26263),
GECAM (GCN 26264), iTelescope T18 (GCN 30265) and SARA-KP (GCN 30268).

The best LAT on-ground location is found to be

(RA, Dec) = 319.7, 33.9 (degrees, J2000)

with an error radius of 0.13 deg (90% containment, statistical error 
only). This position
is consistent with the XRT localization (GCN 30267). The location of the 
GRB was outside
the LAT FoV at the time of the trigger (T0 = 23:59:25 UT on 2021-06-19) 
and came into
view at T0+200 s.

The data from the Fermi-LAT show a significant increase  in the event 
rate that is spatially
correlated with the Swift emission with high significance. The highest 
energy photon is a
8.3 GeV event detected ~410 s after the trigger.

The photon flux above 100 MeV in the time interval 200-1000 s after the 
Swift trigger is
(1.6 +/- 1.2) e-06 ph/cm2/s.

The estimated photon index above 100 MeV is -1.5 +/- 0.3.

The Fermi-LAT point of contact for this burst is
Roberta Pillera (roberta.pillera at ba.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.