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R. Tanabe (Tokyo Gakugei University), J. Watanabe (NAO), H. Boehnhardt, C.E. Delahodde, O.R. Hainaut (ESO/Chile), H. Rauer (DLR), F. Marchis (IAS/Paris)
We are monitoring comet C/1995~O1 (Hale-Bopp) since its passage through perihelion. The data we present here were obtained from Sep.~1997 till Apr.~2000 on the 1.5m Danish, 2.2m ESO/MPI, 3.6m, NTT, and VLT telescopes at ESO's observatories. This extensive collection of R frames were processed and enhanced in order to reveal details in the coma structure.
On various epochs in January and February 1998, while the comet was at r=7.5AU, secondary condensations were observed at ~15'' ~q 5.104 km from the main nucleus, but were not visible anymore in March 1998. These condensations are accompanied by an independent coma, and are interpreted as fragments detached from the nucleus.
We will present these data and the enhancement techniques that were used, as well as discuss the nature and evolution of the fragments, putting them in the perspective of the secondary nucleus observed by Marchis et al. (1999, A&A 349, p. 985) using adaptive optics.