TITLE: GCN CIRCULAR NUMBER: 9934 SUBJECT: GRB 090926: Fermi LAT detection DATE: 09/09/26 19:39:23 GMT FROM: Takeshi Uehara at Hiroshima U GRB 090926: Fermi LAT detection Takeshi Uehara, Hiromitsu Takahashi (Hiroshima University) and Julie McEnery (NASA/GSFC) report on behalf of the Fermi LAT team: At 04:20:26.99 (UT) on 26 Sep 2009, the Fermi Large Area Telescope (LAT) detected gamma rays from the long GRB 090926, which was triggered and located by the Fermi Gamma-ray Burst Monitor (GBM) (trigger 275631628 / 090926181, GCN9933). The angle of the GBM best position (RA, Dec= 354.5, -64.2) with respect to the LAT boresight was ~52 degrees at the time of the trigger, which is close the edge of our field of view. The data from the Fermi LAT shows a significant increase in the event rate within 2.5 degrees of the GBM location 7 s after the GBM trigger that is spatially and temporally correlated with the GBM emission with high significance. More than 150 photons above 100 MeV and more than 20 photons above 1 GeV are observed up to more than 200 s after the GBM trigger. The highest energy photon is a 19.6 GeV event which is observed 26 seconds after the GBM trigger. The best LAT on-ground localization is found to be (RA, Dec = 353.56, -66.34) with a 90% containment radius of 0.07 deg (statistical; 68% containment radius: 0.04 deg, preliminary systematic error is less than 0.1 deg) which is consistent with the GBM localization. A Swift TOO request has been issued. Further analysis is ongoing. The points of contact for this burst is Takeshi Uehara : uehara@hep01.hepl.hiroshima-u.ac.jp 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. This message can be cited.