On the separation we may choose

There are two radius in this simulation with respect to the AGB star: dust sublimation radius, L1 point radius.

The dust sublimation radius is calculated by:

where represent the photon absorption efficiency. is the AGB star's luminosity. is the Stefan-Boltzmann constant. is the dust sublimation temperature.

A major question is, what is the value of ? I choose because some dust only absorb optical and ultraviolet wavelength photon e.g. MgSiO3. However, iron based silicates can absorb NIR photon efficiently. On the other hand, the self-extinction can redden the SED a lot. At last, a cool atmosphere should be assumed in the first place, e.g. 3000 K or so.

Usually the dust formation radii is around (I saw it somewhere). If I choose the photosphere of the AGB star to be around then the dust formation radii can be around

Let me list my chose of parameters:

This will give

If we choose then the radii of L1 points are:

Therefore, case a is the only one that may be different from the others. But it is not necessary that case one must have different mass transfer behavior. Because the separation is still larger than the dust sublimation radii, in the current model, the radiative force on the fluid may blow away the disk or any structure around the secondary. If one want to see the disk around the secondary, the radiative ray tracing algorithm should be 3-D. Besides, the dust sublimation around the secondary should also be considered.

Difference between iron deficit and iron rich amorphous dust can be found here.

​Jena dust database

The AGB star is put into the simulation. In high resolution simulation, a circumbinary disk can form with separation

topdensity.gif​

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