Letter to the Editor

INTEGRAL results on GRB 030320: A long gamma-ray burst detected at the edge of the field of view^*

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
² Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
³ INTEGRAL Science Data Centre, Chemin d'Écogia 16, 1290 Versoix, Switzerland
⁴ INAF / Brera Astronomical Observatory, via E. Bianchi 23807, Merate (LC), Italy
⁵ Istituto di Astrofisica Spaziale e Fisica Cosmica – CNR, Sezione di Milano “G. Occhialini”, via Bassini 15, 20133 Milano, Italy
⁶ Dipartimento di Fisica, Università degli Studi di Milano Bicocca, P.zza della Scienza 3, 20126 Milano, Italy
⁷ International School for Advanced Studies (SISSA-ISAS), via Beirut 2–4, 34014 Trieste, Italy
⁸ Code 661, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁹ Universities Space Research Association, 7501 Forbes Blvd. #206, Seabrook, MD 20706, USA

Corresponding author: A. von Kienlin, azk@mpe.mpg.de

Received: 16 July 2003
Accepted: 8 August 2003

Abstract

GRB 030320 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 . The peak flux in the 20–200 keV band is determined to ~5.7 photons cm^-2 s^-1 and the GRB fluence to  erg cm^-2. 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.