Title:Disks Surrounding Massive Stars: when computational models are confronted by observations

Abstract:
Many massive stars are embedded within gaseous circumstellar matter; sometimes dust and molecules 
are also present. Though the disks are sometimes too small to be detected directly, this material 
can be detected in the spectrum of radiation we observe from the star. Often, the circumstellar 
material has a disk-like distribution, but the physical processes that form and maintain these 
disks are not well understood. Be stars are an example of rapidly rotating, hot stars, whose 
spectra at optical wavelengths show both hydrogen emission lines and, frequently, emission lines 
from singly ionized metals due to the presence of a disk.

We have computed theoretical models of circumstellar disks for Be stars, using a non-LTE radiative 
transfer code which incorporates a number of improvements over previous treatments of the disk 
thermal structure, including a realistic chemical composition. These models can predict spectral 
line profiles and equivalent widths, spectral energy distributions, and continuum polarization. 
Models with accurate thermal structures and radiation fields are essential to interpreting 
observations correctly. These models can also predict images on the plane of the sky in important 
wavelengths and are therefore ideally suited for comparison with interferometric observations. I 
will demonstrate that our models can be constrained by direct comparison with optical 
interferometric observations for the Halpha emitting region and by contemporaneous Halpha 
line profiles. Detailed comparisons of our predictions with H! interferometry and spectroscopy 
place very tight constraints on the model free parameters for these star-disks systems.