EDP Sciences
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Volume 378, Number 1, October IV 2001
Page(s) 76 - 81
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011203

A&A 378, 76-81 (2001)
DOI: 10.1051/0004-6361:20011203

Limits on the early afterglow phase of gamma-ray burst sources from TAROT-1

M. Boër1, J. L. Atteia1, M. Bringer1, B. Gendre1, A. Klotz1, R. Malina2, J. A. de Freitas Pacheco3 and H. Pedersen4

1  Centre d'Étude Spatiale des Rayonnements (CNRS/UPS), BP 4346, 31028 Toulouse Cedex 4, France
2  Laboratoire d'Astrophysique de Marseille (CNRS/OAMP), Traverse du Siphon, BP 8, 13376 Marseille Cedex 12, France
3  Observatoire de la Côte d'Azur, BP 229, 06304 Nice Cedex 4, France
4  NBIfAFG, Copenhagen University Observatory, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark

(Received 30 October 2000 / Accepted 9 August 2001 )

The Télescope à Action Rapide pour les Objets Transitoires (TAROT-1) has as its prime objective the observation of the prompt and delayed emission of cosmic gamma-ray bursts (GRBs). We have performed a search for optical emission from 6 GRBs detected by BATSE. The positioning error circle was fully covered within typically thirty minutes after the trigger. No detection of the early afterglow phase was made, and magnitude limits in the range of mR = 13-15 were estimated using 20 s exposures. These limits are compared to optical afterglow data obtained in later phases and the results are interpreted in terms of source distances. They correspond to a median redshift of z = 0.5. With HETE-2 and the planned instrument upgrade, TAROT-1 will be able to detect the early optical emission of GRBs up to a redshift of the order of 5.

Key words: gamma-ray: bursts

Offprint request: M. Boër, Michel.Boer@cesr.fr

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