Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets

¹ Department of Physics, State University of Londrina, Perobal, 86051 Londrina, PR, Brazil
² Southwest Research Institute, 6220 Culebra Road, P. O. Drawer 28510, San Antonio, TX 78228-0510, U.S.A. e-mail: Walter.huebner@hq.nasa.gov
³ On leave from Department of Astronomy, Institute of Astronomy and Geophysics, University of São Paulo, Av. Miguel Stefano 4200, Agua Funda, São Paulo, Cep. 04301-904, Brazil

Send offprint request to: W.F. Huebner

Received: 9 February 1995
Accepted: 22 March 1996

Abstract

In an attempt to find correlations between properties of comets, we determine the dust colors, dust release rates, and dust-to-gas mass ratios in the comae of Comets Bowell (1980 b = 1982 I), Bradfield (1979 l = 1979 X), Brorsen-Metcalf (1989 o = 1989 X), Giacobini-Zinner (1984 e = 1985 XIII), Levy (1990 c = 1990 XX), and Stephan-Oterma (1980 g = 1980 X) using a uniform and systematic analysis of the continuum fluxes measured at optical wavelengths. We assume that the continuum fluxes observed in these comets are from light scattered by micrometer-sized dust particles. The color of the dust is blue, relative to the Sun, in Comets Bradfield (1979 X) and Brorsen-Metcalf (1989 X); both comets have a low dust-to-gas mass ratio (). Comets Giacobini-Zinner (1985 XIII) and Stephan-Oterma (1980 X) have an intermediate dust-to-gas mass ratio (), whereas Comets Levy (1990 XX) and Bowell (1982 I) have a high dust-to-gas mass ratio (). The continuum flux from dust particles in comets with intermediate to high dust-to-gas mass ratios is in general red, relative to the Sun. However, the color changes to blue in these comets when the dust-to-gas mass ratios are low relative to their peak values.