The IRC +10216 circumstellar envelope. II - Spatial measurements of the dust

Abstract

A detailed study has been performed of the spatial structure of the IRC +10216 dust shell in the wavelength range 1-5 microns. An occultation observed at 4.6 microns is deconvolved to provide a one-dimensional image. A radiometric analysis of the dust shell flux distribution is performed based on coeval photometry, leading to an estimate of the shell extinction, a decomposition of the flux into shell and stellar components, and an estimate of the temperature of the dust at the inner boundary of the shell. A simple, nonequilibrium, geometrical model of the shell is used to estimate the inner radius of the dust envelope, and detailed radiative equilibrium models based on realistic opacities and a two-component grain population are developed. The best estimates of model parameters are selected, and the limiting factors in the analysis are discussed.