Light-scattering models applied to circumstellar dust properties

Radiation pressure force, Poynting-Robertson effect, and collisions are important to determine the size distribution of dust in circurnstellar debris disks with the two former parameters depending on the light- scattering properties of grains. We here present Mie and discrete-dipole approximation (DDA) calculations to describe the optical properties of dust particles around beta Pictoris, Vega, and Fomalhaut in order to study the influence of the radiation pressure force. We find that the differences between Mie and DDA calculations are lower than 30% for all porosities. Therefore, Mie calculations can be used to determine the cut-off limits which contribute to the size distribution for the different systems. (C) 2004 Published by Elsevier Ltd.