2007ApJ...663..543H

We present observations and modeling of a lunar occultation of the dust-enshrouded carbon star AFGL 5440. The observations were made over a continuous range of wavelengths from 1 to 4 µm with a high-speed spectrophotometer designed expressly for this purpose. We find that the occultation fringes cannot be fit by any single-size model. We use the DUSTY radiative transfer code to model a circumstellar shell and fit both the observed occultation light curves and the spectral energy distribution described in the literature. We find a strong constraint on the inner radius of the dust shell, T_max=950±50 K, and optical depth at 5 µm of 0.5±0.1. The observations are best fit by models with a density gradient of ρ∝r^–2 or the gradient derived by Ivezi{cacute} & Elitzur for a radiatively driven hydrodynamic outflow. Our models cannot fit the observed IRAS 60 µm flux without assuming a substantial abundance of graphite or by assuming a substantially higher mass-loss rate in the past.