Early Optical Observations of Grbs by the Tarot Telescopes: Period 2001-2008

The TAROT telescopes (Télescopes à 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 sec 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. Subject headings: telescope: general — GRBs: individual ( GRB 010213, GRB 020531, GRB 030115, GRB 030324, GRB 030329, GRB 030501, GRB 040916, GRB 041006, GRB 041218, GRB 041219A, GRB 050209, GRB 050306, GRB 050408, GRB 050416, GRB 050504, GRB 050505, GRB 050520, GRB 050525A, GRB 050730, GRB 050803, GRB 050824, GRB 050904, GRB 051211A, GRB 051211B, GRB 051221B, GRB 060111A, GRB 060111B, GRB 060124, GRB 060512, GRB 060515, GRB 060814, GRB 060904A, GRB 060904B, GRB 060919, GRB 061019, GRB 061027, GRB 061028, GRB 061110B, GRB 061217, GRB 061218, GRB 061222B, GRB 070103, GRB 070227, GRB 070330, GRB 070411, GRB 070412, GRB 070420, GRB 070508, GRB 070521, GRB 070621, GRB 070628, GRB 070913, GRB 070920A, GRB 070920B, GRB 071010A, GRB 071101, GRB 071109, GRB 071112B, GRB 071112C, GRB 080129, GRB 080207, GRB 080210, GRB 080315, GRB 080330, GRB 080413A, GRB 080430, GRB 080516, GRB 080603B, GRB 080903 ) — 1