GCN Circular 37418
Subject
GRB 240905B: Fermi-LAT detection
Date
2024-09-07T03:07:29Z (2 months ago)
Edited On
2024-09-07T03:35:06Z (2 months ago)
From
Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Via
email
R. Gupta (NASA GSFC), N. Di Lalla (Stanford University), and D. Kocevski (NASA/MSFC) report on behalf of the Fermi-LAT Collaboration:
On Sep 05, 2024, Fermi-LAT detected high-energy emission from GRB 240905B, which was also detected by Fermi-GBM (trigger 747203241.139826 / 240905186), and AstroSat CZTI (GCN 37391).
The best LAT on-ground location is found to be:
RA, Dec = 268.0, 14.2 (J2000)
with an error radius of 0.2 deg (90 % containment, statistical error only).
This was 28 deg from the LAT boresight at the time of the GBM trigger: T0 = 04:27:16 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 0-10 s after the GBM trigger is (2.2 +/- 0.6) E-4 ph/cm2/s. The estimated photon index above 100 MeV is -2.0 +/- 0.3.
The highest-energy photon is a 3 GeV event which is observed ~ 1.1 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.