We model the infrared ( IR ) emission from the double-ring disk of { HD 141569 A } , using a porous dust model that was previously shown successful in reproducing the spectral energy distributions ( SEDs ) of the disks around \beta Pictoris and { HR 4796 A } .
The dust consists of either unaltered or highly processed interstellar materials and vacuum with a volume fraction of \sim 90 \% .
Together with a population of polycyclic aromatic hydrocarbon ( PAH ) molecules of which a large fraction is charged , the porous dust model made of coagulated but otherwise unaltered protostellar interstellar grains provides an excellent fit to the entire SED from the mid-IR to millimeter wavelengths including the PAH mid-IR emission features .
The nondetection of the 21 { \mu m } crystalline silicate feature predicted from the porous dust model composed of highly-processed grains ( mainly crystalline silicate dust ) imposes an upper limit of \sim 10 \% on the mass fraction of crystalline silicates .
Spectroscopic and broadband photometric predictions are made for SIRTF observations which will provide further tests of the applicability of the porous dust model to circumstellar disks .