A&A 400, 1021-1030 (2003)
DOI: 10.1051/0004-6361:20030074

Spectral analysis of 35 GRBs/XRFs observed with HETE-2/FREGATE

C. Barraud¹, J.-F. Olive², J. P. Lestrade¹, J.-L. Atteia¹, K. Hurley³, G. Ricker⁴, D. Q. Lamb⁵, N. Kawai^{6, 7}, M. Boer², J.-P. Dezalay², G. Pizzichini⁸, R. Vanderspek⁴, G. Crew⁴, J. Doty⁴, G. Monnelly⁴, J. Villasenor⁴, N. Butler⁴, A. Levine⁴, A. Yoshida^{7, 9}, Y. Shirasaki¹⁰, T. Sakamoto^{6, 7, 11}, T. Tamagawa⁷, K. Torii⁷, M. Matsuoka¹², E. E. Fenimore¹¹, M. Galassi¹¹, T. Tavenner¹¹, T. Q. Donaghy⁵, C. Graziani⁵ and J. G. Jernigan<sup>3

1</sup>  Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, 31400 Toulouse, France
²  C.E.S.R., Observatoire Midi-Pyrénées, 31028 Toulouse Cedex, France
³  UC Berkeley Space Sciences Laboratory, Berkeley CA 94720-7450, USA
⁴  Center for Space Reserach, MIT, Cambridge, MA , USA
⁵  Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
⁶  Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
⁷  RIKEN (Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
⁸  Consiglio Nazionale delle Ricerche (IASF), via Piero Gobetti, 101-40129 Bologna, Italy
⁹  Department of Physics, Aoyama Gakuin University, Chitosedai 6-16-1 Setagaya-ku, Tokyo 157-8572, Japan
¹⁰  National Astronomical Observatory, Osawa 2-21-1, Mitaka, Tokyo 181-8588 Japan
¹¹  Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM, 87545, USA
¹²  Tsukuba Space Center, National Space Development Agency of Japan, Tsukuba, Ibaraki, 305-8505, Japan

(Received 21 June 2002 / Accepted 13 January 2003 )

Abstract
We present a spectral analysis of 35 GRBs detected with the HETE-2 gamma-ray detectors (the FREGATE instrument) in the energy range 7-400 keV. The GRB sample analyzed is made of GRBs localized with the Wide Field X-ray Monitor onboard HETE-2 or with the GRB Interplanetary Network. We derive the spectral parameters of the time-integrated spectra, and present the distribution of the low-energy photon index, alpha, and of the peak energy, . We then discuss the existence and nature of the recently discovered X-Ray Flashes and their relationship with classical GRBs.

Key words: gamma-rays: bursts

Offprint request: C. Barraud, barraud@ast.obs-mip.fr

SIMBAD Objects

© ESO 2003

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.