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GCN Circular 17864

GRB 150523A: Fermi-LAT detection
2015-05-23T18:20:18Z (9 years ago)
Elisabetta Bissaldi at U.Innsbruk/IAPP <>
E. Bissaldi (INFN Bari), G. Vianello (Stanford University)
and M. Yassine (LUPM) report on behalf of the Fermi-LAT team:

At 09:29:48.08 UT on May 23, 2015, Fermi-LAT detected
high-energy emission from GRB 150523A, which was also
detected by Fermi-GBM (trigger 454066191 / 150523396)
(Yu et al., GCN #17863).
The best LAT on-ground location is found to be

RA, Dec = 115.36, -45.40 (J2000)

with an error radius of 0.10 deg (90 per cent containment,
statistical error only).
This was 26 deg from the LAT boresight at the time of
the trigger and triggered an autonomous
repoint of the spacecraft.

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 highest-energy photon is a 7 GeV event, which is
observed 118 s 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 (

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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