We present mid-infrared Spitzer-IRS spectra of the well-known UX Orionis star VV Ser .
We combine the Spitzer data with interferometric and spectroscopic data from the literature covering UV to submillimeter wavelengths .
The full set of data are modeled by a two-dimensional axisymmetric Monte Carlo radiative transfer code .
The model is used to test the prediction of ( ) that disks around UX Orionis stars must have a self-shadowed shape , and that these disks are seen nearly edge-on , looking just over the edge of a puffed-up inner rim , formed roughly at the dust sublimation radius .
We find that a single , relatively simple model is consistent with all the available observational constraints spanning 4 orders of magnitude in wavelength and spatial scales , providing strong support for this interpretation of UX Orionis stars .
The mid-infrared flux as measured by Spitzer-IRS is declining and exhibits weak silicate emission features , consistent with a self-shadowed geometry .
MIPS and SCUBA imaging shows that the disk has a small grain dust mass as low as 0.8 \times 10 ^ { -7 } M _ { \odot } .
The low apparent dust mass may be due to strong grain growth and settling .
Further evidence for this is provided by the fact that the grains in the upper layers of the puffed-up inner rim must be small ( 0.01–0.4 \mu m ) to reproduce the colors ( R _ { V } \sim 3.6 ) of the extinction events , while the shape and strength of the mid-infrared silicate emission features indicate that grains in the outer disk ( > 1-2 AU ) are somewhat larger ( 0.3–3.0 \mu m ) .
From the model fit , the location of the puffed-up inner rim is estimated to be at a dust temperature of 1500 K or at 0.7–0.8 AU for small grains .
This is almost twice the rim radius estimated from near-infrared interferometry .
Since larger ( more grey ) grains are able to penetrate closer to the star for the same dust sublimation temperature , a plausible interpretation of the data is that these larger grains have settled to the disk mid-plane in the puffed-up inner rim .
A best fitting model for the inner rim in which large grains in the disk mid-plane reach to within 0.25 AU of the star , while small grains in the disk surface create a puffed-up inner rim at \sim 0.7 - 0.8 AU , is able to reproduce all the data , including the near-infrared visibilities .