They have thin envelopes with analogous dimensions. We have obtained our best fits using a two homogeneous grains code for 3 stars. Cas presents an absorption at about 14 m, which is usually seen in J-type carbon stars, and it's difficult to distinguish between the models. SS Vir shows features at about 8 m and 14 m, too. This figure shows best models for SS Vir, which belongs to Broad 1 class and AZ Aur to Broad 2 class.
Triangles represent the photometric data.
Both objects are very well studied and supposed to have asymmetrical dust envelopes. They are believed to be in the latest stages of stellar carbon evolution. We will discuss them below. Deep B and V image-bands, reveal its extended circumstellar envelope in the dust scattered and show an episodic mass loss rate. 5a and 5b.