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GCN Circular 14574

GRB 130504C: Fermi-LAT detection of a burst
2013-05-05T16:40:11Z (11 years ago)
Daniel Kocevski at SLAC <>
D. Kocevski (NASA/GSFC), M. Ohno (Hiroshima U.), J. Racusin (NASA/GSFC), G. Vianello (Stanford), V. Vasileiou (LUPM), and E. Troja (CRESST) report on behalf of the Fermi-LAT team:

At 23:30:15 UT on 04 May 2013, Fermi LAT detected high energy emission from GRB 130504C, which was also detected by Fermi-GBM (trigger 389402940 / 130504979).  The GBM detection triggered an autonomous repoint of the spacecraft.

The best LAT on-ground location is found to be RA=91.715, DEC=3.846 (J2000) with an error radius of 0.155 deg (68% containment, statistical error only). 

The burst was about 40 deg from the LAT boresight at the time of the trigger and the spacecraft slew brought the source within the LAT field of view for the next 2200 seconds. The data from the Fermi LAT show long lasting emission with >70 photons above 100 MeV observed out to 1000s seconds with a TS of >70.  Multi-peaked emission lasting roughly 40 seconds can be seen using the non-standard LAT Low Energy (LLE) with a significance of ~26 sigma. The highest energy LAT photon has an energy of ~5 GeV arriving 251 seconds after the trigger.

A Swift TOO request has been submitted.

A GBM circular is forthcoming.

The Fermi LAT point of contact for this burst is Daniel Kocevski (

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.

Daniel Kocevski
NASA Goddard Space Flight Center
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