Early optical observations of GRBs by the TAROT telescopes: period
  2001-2008
  The TAROT telescopes (Telescopes a Action Rapide pour les Objets
Transitoires) are two robotic observatories designed to observe the prompt
optical emission counterpart and the early afterglow of gamma ray bursts
(GRBs). We present data acquired between 2001 and 2008 and discuss the
properties of the optical emission of GRBs, noting various interesting results.
The optical emission observed during the prompt GRB phase is rarely very
bright: we estimate that 5% to 20% of GRBs exhibit a bright optical flash
(R<14) during the prompt gamma-ray emission, and that more than 50% of the GRBs
have an optical emission fainter than R=15.5 when the gamma-ray emission is
active. We study the apparent optical brightness distribution of GRBs at 1000 s
showing that our observations confirm the distribution derived by other groups.
The combination of these results with those obtained by other rapid slewing
telescopes allows us to better characterize the early optical emission of GRBs
and to emphasize the importance of very early multi-wavelength GRB studies for
the understanding of the physics of the ejecta.
