TITLE: GCN CIRCULAR NUMBER: 14282 SUBJECT: GRB 130310A: Fermi-LAT detection and localization DATE: 13/03/11 07:36:13 GMT FROM: Sylvain Guiriec at UAH S. Guiriec (NASA/GSFC/NPP), G. Vianello (Stanford) and M. Ohno (Hiroshima U.) report on behalf of the Fermi-LAT team: The Fermi Large Area Telescope (LAT) detected emission from GRB 130310A (GBM trigger 130310840/384638984) at approximately 20:09:44 UT on March 10th, 2013, about 3s after Fermi-GBM trigger time. The burst location was outside the LAT nominal field of view, at an angle of ~79 degrees from the LAT boresight, and ~50 degrees from the Zenith. Using the non-standard LAT Low Energy (LLE) data selection, featuring a large effective area and a larger field of view below 100 MeV but a much larger PSF with respect to the standard classes, we clearly detect the prompt emission of the GRB (significance > 10 sigma above the background). With this selection and in this energy range the GRB shows a single FRED-like pulse, peaking ~3 s after the GBM trigger in good coincidence with the peak of the GBM emission. The high peak flux of the burst triggered an Autonomous Repointing Request (ARR) starting about 50s after the trigger time, which placed the GRB within the LAT nominal field of view for standard data classes (~65 deg) approximately 200 s after the trigger. Using the P7SOURCE_V6 class we detect ~18 photons between 100 MeV and 3 GeV in the time interval 200 s - 800 s from the trigger, clearly clustered in a point source ~4.8 deg away from the best GBM position and with a significance larger than 5 sigma. Our best localization is: R.A., Dec = 142.34, -17.23 (J2000) 90 % containment radius (statistical only) = 0.45 deg. A GBM circular on GRB 130310A is forthcoming. The Fermi LAT point of contact for this burst is Sylvain Guiriec (sylvain.guiriec@nasa.gov)