[vsnet-grb-info 23145] GRB190731A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25244
SUBJECT: GRB190731A: Fermi-LAT detection
DATE:    19/08/01 06:50:53 GMT
FROM:    Masanori Ohno at Hiroshima University  <ohno at astro.hiroshima-u.ac.jp>

M. Ohno (Hiroshima Univ.), F. Longo (University and INFN, Trieste),
M. Arimoto (Kanazawa Univ.), M.  Axelsson (KTH and Stockholm Univ.), and F.
Dirirsa (Univ. of Johannesburg)
report on behalf of the Fermi-LAT team:

On July, 31, 2019 Fermi-LAT detected high-energy emission from GRB 190731A,
which was also detected by Fermi-GBM (Fermi GBM Team, GCN 25240).

The best LAT on-ground location is found to be

RA, Dec = 339.94, -76.62 (J2000)

with an error radius of 0.28 deg (90 % containment, statistical error only).
This was 40 deg from the LAT boresight at the time of the GBM trigger:

T0 =  22:38:20 UT.

 The data from the Fermi-LAT show a significant increase
in the event rate after the GBM trigger that is spatially correlated with
the
GBM emission with high significance.
The photon flux above 100 MeV in the time interval 0-800 s after the
GBM trigger is (1.91 +/- 0.65)E-5 ph/cm2/s.
The highest-energy photon in this interval is a 3.8 GeV event observed
at T0 + 234 s.
The estimated photon index above 100 MeV is -2.17 +/- 0.26.

The Fermi-LAT point of contact for this burst is Masanori Ohno
(ohno at astro.hiroshima-u.ac.jp).

 A Swift ToO has been approved for this burst.


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.