Activity of Comet Tabur (C/1996 Q1) during September 12–17, 1996

Author： Lara L.M. Schulz R. Stüwe J.A. Tozzi G.P.

ISSN： 0019-1035

Source： Icarus, Vol.150, Iss.1, 2001-03, pp. : 124-139

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Abstract

We have obtained and analyzed narrow (CN and continuum) and broadband (B, V, R) CCD images and long-slit spectra of the coma of Comet C/Tabur (1996 Q1), which is a fragment of a split comet together with C/Liller (1988 A1). The observations were taken on Sept. 12–17, 1996, before its first perihelion passage. A detailed structural analysis of the CN images revealed the presence of a double jet structure, shells, and a higher emission on the dayside of the comet that can be attributed to an active area. All of these structures in CN have no counterparts on the dust. The broadband images showed the same double jet structure with an overimposed dust tail. The CN and C₂ production rates, as well as the dust production rate deduced from the customary Afρ, show a steady increase during the five days the comet was monitored, reaching a maximum on Sept. 14. The surface brightness profiles of the continuum, either from the images or from the long-slit spectra, show a very steep gradient (1.67≤m≤2.25) at projected radial distances (ρ) shorter than 3200 km in the Sun direction, whereas at ρ>3200 km all continuum profiles can be well fitted with m≈1 in log B-log ρ representation. The shape of the brightness profiles follows the same pattern during five consecutive days, unlike the flux, which differs from Sept. 13 to 14 and from Sept. 14 to 16. Further analysis of the reflectivity variations proves that the reflectance of the dust behaves differently in the Sun and in the tail directions. The continuum light scattered from the dust in the coma of Comet Tabur is bluest at ρ∼1800 km east photocenter (i.e., Sun direction), whereas westward the reflectivity of the dust can be regarded as constant at every ρ. The reflectivity variations are much the same in all spectra of Comet Tabur on Sept. 13–16. In principle, the data can be interpreted as the progressive destruction (either by fragmentation and/or by ice sublimation) of the grains in the dust coma of the comet. As Comet Tabur is probably a fragment of a split comet (Marsden 1996a,b), it might have released fresh, less processed material coming from the interior of the nucleus.