TITLE: GCN CIRCULAR NUMBER: 15464 SUBJECT: GRB 131108A: Fermi-LAT onboard detection of a burst DATE: 13/11/08 21:39:17 GMT FROM: Judith Racusin at GSFC J. L. Racusin (NASA/GSFC), S. Zhu (NASA/GSFC/UMD), D. Kocevski (NASA/GSFC/ORAU), M. Ohno (Hiroshima), N. Omodei (Stanford), E. Troja (NASA/GSFC/CRESST) and G. Vianello (Stanford), report on behalf of the Fermi LAT team: At 20:41:55.76 UTC on November 8, 2013, Fermi LAT triggered onboard on high energy emission from GRB 131108A. The burst was also detected by GBM (trigger 131108863/405636118), and triggered an autonomous repoint of the spacecraft. This is the first onboard trigger since 2009, indicating a potentially rare and exciting event. The onboard location is R.A., Dec. 156.47, +9.90 (J2000) with an approximate error radius of 0.5 deg, seeded by the GBM detected position. This was 27 deg from the LAT boresight at the time of the trigger. We anticipate providing a refined location within the next 12-15 hours when the LAT science data for this burst is downlinked and processed. The Fermi LAT point of contact for this burst is Masanori Ohno (ohno@hep01.hepl.hiroshima-u.ac.jp). A Swift TOO request has been approved. 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.