TITLE: GCN CIRCULAR NUMBER: 12989 SUBJECT: GRB 120226A: Fermi-LAT detection of a burst DATE: 12/02/27 13:53:07 GMT FROM: Vlasios Vasileiou at LUPM/Fermi-LAT V. Vasileiou (CNRS/IN2P3/LUPM) and J. L. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: Fermi-LAT has detected high energy emission from GRB 120226A in ground analysis. The GRB was triggered on by Fermi-GBM at 20:54:17.03 on Febuary 26, 2012 (trigger 351982459). The GRB was significantly detected during the prompt phase only using a non-standard LAT data selection most sensitive in the tens-of-MeV energy range, with which over ~50 counts above background were detected within a 60 s interval coinciding with the time of the GBM emission. This data selection has insufficient spatial resolution to provide a reliable LAT localization. However, the GRB became detectable with the standard LAT analysis techniques only after data of longer time scales were accumulated. A preliminary maximum-likelihood analysis of the E>100MeV P7SOURCE_V6 LAT data generated during the first 1.9 ks after the GBM trigger (until the GRB became occulted by the Earth) revealed a source with a ~4 sigma statistical significance, corresponding to ~14 excess events. The source spectrum is best fit with a power law of index -1.6+-0.3. Using this analysis, we obtained the best LAT on-ground localization of: RA(J2000) = 305.30 deg Dec(J2000) = 40.75 deg with an error radius 0.36 deg (90% containment, statistical error only), which is 4 deg from the best GBM localization and ~37 deg with respect to the LAT boresight at the time of the trigger. The GRB triggered an autonomous repoint of the Fermi spacecraft bringing our best localization to ~12 deg from the LAT boresight for 1.9 ks after the trigger. The burst position is close to the Galactic plane at (l,b) = 78.5, 2.3 deg. A Swift TOO has been requested. The Fermi LAT point of contact for this burst is Vlasios Vasileiou (vlasios.vasileiou@lupm.in2p3.fr). 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.