TITLE: GCN CIRCULAR NUMBER: 9021 SUBJECT: Fermi GBM and LAT detections of GRB 090323 DATE: 09/03/23 21:24:41 GMT FROM: Alexander van der Horst at NASA/MSFC Masanori Ohno (ISAS/JAXA), Sara Cutini (ASDC), Julie McEnery (NASA/GSFC), Jim Chiang (SLAC/KIPAC), Elmar Koerding (AIM/Saclay) report on behalf of the Fermi LAT team, and Alexander van der Horst (NASA/MSFC/ORAU) reports on behalf of the Fermi GBM team. "At 00:02:42.63 UT on 23 March 2009, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 090323 (trigger 259459364 / 090323002). The GBM light curve consists of multiple peaks and has a duration of ~150 seconds. The Fermi Large Area Telescope (LAT) has significantly, with more than 5 sigma, detected this GRB. Emission was observed in the LAT up to a few GeV. The high-energy emission commences several seconds after the GBM trigger time, and we see marginal evidence in the LAT that it continues for up to a couple of kilo-seconds. The best LAT on-ground localization is found to be (RA,Dec=190.69, 17.08) with a 68% (resp. 90%) containment radius of 0.09 deg (resp. 0.14, statistical), and a systematic error less than 0.1 deg. The GBM on-ground localization is consistent with this LAT localization within statistical and systematic uncertainties. We further report that the Fermi Observatory executed a maneuver following this trigger and tracked the burst location for the next 5 hours, subject to Earth-angle constraints. Further analysis is ongoing. The points of contact for this burst are Masanori Ohno (LAT, ohno@astro.isas.jaxa.jp) and Alexander van der Horst (GBM, Alexander.J.VanDerHorst@nasa.gov). 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."