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GCN Circular 18065

Subject
GRB 150724B: Fermi-LAT detection
Date
2015-07-25T13:52:53Z (9 years ago)
From
Judith Racusin at GSFC <judith.racusin@nasa.gov>
E. Bissaldi (INFN Bari), J. L. Racusin (NASA/GSFC), and E. Moretti (MPP Munich) 
report on behalf of the Fermi-LAT team: 

At 18:45:36.71 on 2015-07-24, Fermi-LAT detected high-energy emission from GRB 150724B, 
which was also detected by Fermi-GBM (trigger 459456340/150724782). 

The best LAT on-ground location is found to be

RA, Dec = 351.92, 3.67 (J2000) 

with an error radius of 0.3 deg (90% containment, systematic error only). This was 58 deg 
from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a ~5 sigma increase in the event rate within 7 degrees 
of the GBM location after the GBM trigger that is spatially and temporally correlated with the 
GBM emission. More than 11 photons above 100 MeV and 1 photons above 1 GeV were 
observed within 300 seconds. The highest-energy photon is a 2 GeV event which is 
observed ~50 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@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.
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