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GCN Circular 36550

GRB 240527B: Fermi-LAT detection
2024-05-27T23:09:39Z (2 months ago)
Rahul Gupta at NASA/GSFC <>
R. Gupta (NASA/GSFC), F. Longo (University and INFN, Trieste), and A.
Holzmann (DF, University of Buenos Aires, Argentina) report on behalf of
the Fermi-LAT Collaboration:

At 14:03:51.50 on May, 27, 2024 Fermi-LAT detected high-energy emission
from GRB 240527B which was also detected by Fermi-GBM (trigger 738511436 /
240527586, GCN 36546).

The best LAT on-ground location is found to be

RA, Dec = 128.10, -14.48 (J2000)

with an error radius of 0.19 deg (90 % containment, statistical error only).

This was 77 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate
that is spatially and temporally correlated with the trigger with high
significance. The photon flux above 100 MeV in the time interval 0-3000 s
after the GBM trigger is (6.2 +/- 3.0) E-7 ph/cm2/s. The estimated photon
index above 100 MeV is - 1.6+/- 0.2.

The highest-energy photon is a 4.0 GeV event which is observed about
1200 seconds after the GBM trigger.

A Swift ToO has been approved.

The Fermi-LAT point of contact for this burst is Rahul Gupta (

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.

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