Superwind models for the dust shells around OH/IR stars

We have modeled the dust envelopes around OH/IR stars with the changes in the dust density distribution that are expected from a superwind phase. We explore the effect of a superwind due to a helium shell flash by adding a density-enhanced region that proceeds outward. Depending on the position and the degree of the enhancement, the emergent model spectral energy distributions can be significantly different from the ones with the conventional power-law density distributions. The time evolution of the spectral energy distribution of a superwind can, at certain times, explain some observations of OH/IR stars. However, at other times in the evolution of a superwind, spectral energy distributions and optical depths that are not observed often result.