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GCN Circular 14471

Subject
GRB 130427A: Fermi-LAT detection of a burst
Date
2013-04-27T20:10:41Z (11 years ago)
From
Judith Racusin at GSFC <judith.racusin@nasa.gov>
S. Zhu, J. Racusin, D. Kocevski, J. McEnery (NASA/GSFC), F. Longo (Univ of Trieste and INFN), J. Chiang (SLAC), G. Vianello (Stanford) report on behalf of the Fermi-LAT team:

At 07:47:06 UT on 27 April 2013, Fermi LAT detected high energy emission from GRB 130427A, which was also detected by Fermi-GBM (trigger 388741629/130427324) and by Swift (Maselli et al. GCN 14448).  The GBM detection triggered an autonomous repoint of the spacecraft.

The LAT on-ground location is consistent with the optical position reported in Elenin et al. (GCN 14450). The burst was about 47 deg from the LAT boresight at the time of the trigger and within the LAT field of view for the next 700 seconds.

The data from the Fermi LAT show a multi-peaked light curve consistent with the GBM trigger. More than 200 photons above 100 MeV are observed within 100 seconds with a TS of >1000.  Using the non-standard LAT Low Energy (LLE) data selection, thousands of counts above background were detected within a 100 s interval coinciding with the time of the GBM emission, with a significance of ~40 sigma. The highest energy LAT photon has an energy of 94 GeV.

A GBM circular is forthcoming.

The Fermi LAT point of contact for this burst is Sylvia Zhu (s.jc.zhu@gmail.com).

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.

[GCN OPS NOTE(30apr13): Per author's request, time in the first sentence was changed from "07:47:15" to "07:47:06".]
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