GAS AND DUST RELEASE RATES AND COLOR OF DUST IN COMETS P HALLEY (1986-III), P/GIACOBINI-ZINNER (1985-XIII), AND P/HARTLEY-GOOD (1985-XVII)/

CN, C-2, and C-3 emission fluxes observed at wavelengths of 388, 516, and 405 nm in the spectra of the comae of comets P/Halley (1986 III), P/Giacobini-Zinner (1985 XIII), and P/Hartley-Good (1985 XVII) were an alyzed within the framework of the Haser model (Haser, Bull. Acad. R. Belg., Classe de Sciences 43, 740, 1957). Column densities and product ion rates of these gaseous species are determined and compared with th ose from other observations. For pre-perihelion heliocentric distances it is found that production rates/expansion velocity (Q/v) for specie s vary productional to r(-n), where n is 3.7 +/- 0.8, 1.7 +/- 0.7, and 4.7 +/- 1.4 for CN, C-2, and C-3, respectively. Continuum fluxes meas ured at wavelengths of 484.5 and 412.0 nm were analyzed, and dust rele ase rates in the coma of these comets are determined. The dust release rates decrease with increase of heliocentric distance for comet Halle y, and follow a r(-3.07+/-0.7) power law. Color excesses of grains wer e determined in comets P/Hartley-Good (1985 XVII). (C) 1997 Elsevier S cience Ltd.