This object is surrounded by an extended expanding molecular envelope, resulting from extensive mass-loss. Trammell et al. The envelope properties found from molecular line observations by Knapp et al. The best fit can be seen in Figs. 5c and 5d.
Triangles represent the photometric data.
The temperatures of the central stars vary from 2400 K to 2800 K. Inner radii vary between 3 to 4.9 . Y CVn and W CMa. We can see that the emission feature is shifted to longer wavelengths. Our sample of extreme carbon stars contains objects that have optical depths varying between 3.0 and 13. The stars belonging to our E1 group were better described by a two homogeneous grains model.