SPECTROSCOPIC OBSERVATION OF COMET P DE VICO - COMPARISON WITH P/HALLEY AND P/BRORSEN-METCALF/

A spectroscopic observation of Comet P/de Vice in the visible region w as made at Bisei Astronomical Observatory on 1995 October 11. The obta ined spectrum covers the wavelengths from 5200 to 7200 Angstrom, and i ncludes several emissions, such as C-2, NH2, and [O I]. The ratios of the gas-production rates of C-2 and NH2 relative to that of H2O, Q(C-2 )/Q(H2O), and Q(NH2)/Q(H2O), were determined from our observation base d on the Haser model. The production-rate ratio and gas-to-dust ratio were: Q(C-2)/Q(H2O) = 0.25%, Q(NH2)/Q(H2O) = 0.14%, and log(10)[Q(HaO) /Af rho] = 26.9 at the time of observation. Comet P/de Vice was simila r to P/Halley from the viewpoint of the chemical composition (C-2 and NH2 relative to the H2O), and P/de Vice was comparable to P/Brorsen-Me tcalf concerning the gas-to-dust ratio. P/de Vice was one of the most gas-rich comets ever known.