Photoelectric photometry of comet Kohoutek (1973 XII = C/1973 E1): the production rates of CN, C2, and solid refractory particles typical of dynamically new comets

In the past the enterprise to study comet Kohoutek (1973 XII), then called “The Comet of the Century”, was proportionally comparable only with the recent and highly successful one to study comet P/Halley (1986 III). Now over 20 years after this historical endeavour, the original photometric data obtained by Lubos Kohoutek on 14 nights between January 16 and 30, 1974, post-perihelion, when the heliocentric and geocentric distances of the comet were r = 0.66 – 1.00 AU and Δ = 0.81 – 0.96 AU, using the 50 cm (f/15) reflecting telescope of the European Southern Observatory (ESO) in La Silla (Chile) are analysed. Emission fluxes of the bright 388.4 nm CN (0,0) band, the prominent 473.7 nm C2 (1,0) and 517.2 nm C2 (0,0) Swan bands, and the 530.0 nm red continuum are studied in the framework of Haserʹs isotropic radial outflow model. Parent gas production rates of CN, C2, and the gas-to-dust (Afϱ parameter) ratio for each observation is determined. An average gas mass loss dMgdt ≈ 1675 kg s−1 is estimated. Using the single particle dust model of Richter and Keller (Astron. Astrophys. 206, 136–142, 1988) an average total dust production rate dMddt = 1.6 × 104 kg s−1 is calculated, and the average emission lifetimes in the coma for small (a1 = 0.6 μm) and large (a2 = 600 μm) particles have been estimated in about 2 days (≈ 1.70 × 105s) and 2 months (≈ 5.36 × 106s), respectively, for a coma of radius R = 2 × 105 km.