Dust Activity of Comet Hale-Bopp (C/1995 O1) at R tex2html_wrap_inline18 tex2html_wrap_inline20 3 AU

G. P. Tozzi (OAA), F. Mannucci (CNR-CAISMI), R. Stanga, L. Testi (UniFI)

Observations of comet Hale-Bopp (C/1995 O1) have been performed in the infrared (J, H, K bands) at the Nordic Optical Telescope (NOT), located on Canary islands, with the ARNICA (ARcetri Near Infrared CAmera). The comet was observed during two periods, at the beginning and the end of September 1996, when the comet was at heliocentric distances r tex2html_wrap_inline18 of tex2html_wrap_inline20 3.3 and 2.9 AU, respectively. The data show a relatively large activity of the comet with production of some outbursts, the largest of which happened some time before the start of the second run (24.8 Sept.) and which may be the further evolution of the outburst detected by the HST (Weaver et al., 1997, Science 275, 1900). Here we present the analysis of the data with particular attention to the evolution of the outbursts and the photometric IR color index of the dust released.