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GCN Circular 17667

GRB 150403A: Fermi-LAT detection
2015-04-04T10:12:54Z (9 years ago)
Elisabetta Bissaldi at U.Innsbruk/IAPP <>
F. Longo (University & INFN Trieste), E. Bissaldi (INFN Bari),
M. Arimoto (Tokyo Tech) and S. Zhu (UMD, USA)
report on behalf of the Fermi-LAT team:

At 21:54:10.95 on April 03, 2015, Fermi-LAT detected
high-energy emission from GRB 150403A, which was also
detected by Fermi-GBM (trigger 449790853/150403913)
and Swift (Lien at al, GCN 17665).

The GBM location was initially inside the LAT field
of view at an angle of ~55 degrees to the LAT boresight
and triggered an autonomous repoint of the spacecraft.

The best LAT on-ground location is found to be

RA, Dec (J2000)   311.79, -62.76

with an error radius of  0.50 deg (95% containment,
statistical error only) and consistent with the
enhanced Swift/XRT location (Beardmore et al, GCN 17666).

The data from the Fermi-LAT show a significant increase
in the event rate within 12 degrees of the Swift/XRT
location after the trigger.
More than 30 photons above 100 MeV are observed
within 2000 seconds. The highest-energy photon is a
5 GeV event which is observed 630 s after the GBM trigger.

Using the LAT Low Energy (LLE) data selection, over 200 counts
above background are detected within a 20 s interval coincident
with the time of the GBM emission.

The Fermi-LAT point of contact for this burst is
Sylvia Zhu (

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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