INTEGRAL results on GRB 030320 : a long gamma - ray burst detected at the edge of the field of view ⋆

GRB030320 is the 5th Gamma-ray burst (GRB) detected by INTEGRAL in the field of view (FoV). It is so far the GRB with the largest off-axis angle with respect to the INTEGRAL pointing direction, near to the edge of the FoV of both main instruments, IBIS and SPI. Nevertheless, it was possible to determine its position and to extract spectra and fluxes. The GRB nature of the event was confirmed by an IPN triangulation. It is a ∼ 60 s long GRB with two prominent peaks separated by ∼ 35 s. The spectral shape of the GRB is best represented by a single power law with a photon index Γ ≃ 1.7. The peak flux in the 20 – 200 keV band is determined to ∼ 5.7 photons cm s and the GRB fluence to 1.1× 10 erg cm. Analysing the spectral evolution of the GRB, a “hard-to-soft” behaviour emerges. A search for an optical counterpart has been carried out, but none was found.