Optical colours and polarization of a model reflection nebula IV. Mixture of grains in the case of the star within the nebula

Abstract

The UBV colour differences and polarization that can be caused by mixtures of interstellar grains in a model reflection nebula have been presented. The geometrical configuration of the nebula is adapted in the form of a homogeneous plane-parallel slab with the star within the nebula. The materials of the grain species include ice, graphite, enstatite silicate and silicon carbide. We have considered separately one-, two-, and three-component mixtures of the grains in various proportions of their number densitits. Each of the grain species follows an exp (-a(power 3))-type size distribution function. The wavelength dependent indices of refraction have been used throughout.