GCN Circular 9044

Julie McEnery (NASA/GSFC), Sara Cutini (ASDC), Masanori Ohno (ISAS/JAXA)  and Elmar Koerding (AIM/Saclay) report on behalf of the Fermi LAT  collaboration and Valerie Connaughton (UAH) reports on behalf of the 
Fermi GBM collaboration

At 09:36.46 UT on 28 March 2009, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 090328 (trigger 259925808 / GRB090328401). The  GBM lightcurve shows a multi-peaked event, with the brightest set of peaks occurring within 50 sec and a further peak at 60 sec tailing off  beyond 100 sec post-trigger. The burst is detected at least to 1 MeV.

The Fermi Large Area Telescope (LAT) has significantly detected this GRB. Emission was observed in the LAT up to a few GeV with a detection  significance of more than 5 sigma.

The current best LAT on-ground localization is found to be (RA,Dec=90.87, -41.95) with a 68% containment radius of 0.11 deg, 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.

Swift TOO observations have been requested at the LAT measured position.

Further analysis is ongoing.

The points of contact for this burst are Julie McEnery (LAT, julie.mcenery@nasa.gov) and Valerie Connaughton (GBM, valerie@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.

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