GCN Circular 37331
Subject
GRB 240828A: Fermi-LAT detection
Event
Date
2024-08-29T01:53:02Z (a year ago)
From
Rahul Gupta at NASA GSFC <rahulbhu.c157@gmail.com>
Via
email
R. Gupta (NASA GSFC), and N. Di Lalla (Stanford University) report on
behalf of the Fermi-LAT Collaboration:
On Aug 28, 2024, Fermi-LAT detected high-energy emission from GRB 240828A,
which was also detected by Fermi-GBM (trigger 746549711 / 240828622, GCN
37317), and AstroSat CZTI (GCN 37328).
The best LAT on-ground location is found to be:
RA, Dec = 225.49, 36.64 (J2000)
with an error radius of 0.30 deg (90 % containment, statistical error only).
This was 93 deg from the LAT boresight at the time of the GBM trigger: T0 =
14:55:06 UT.
The data from the Fermi-LAT show a significant increase in the event rate
that is spatially and temporally correlated with the GBM emission with high
significance. The photon flux above 100 MeV in the time interval 3500-6100
s after the GBM trigger is (8.2 +/- 3.8) E-7 ph/cm2/s. The estimated photon
index above 100 MeV is -2.1 +/- 0.4.
The highest-energy photon is a 1.7 GeV event which is observed ~ 5400
seconds after the GBM trigger.
A Swift ToO has been approved for this burst.
The Fermi-LAT point of contact for this burst is Niccolo' Di Lalla (
niccolo.dilalla@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.