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L. Hutchison (MIT), S. Desch (DTM)
We place constraints on the composition of the dust in the protoplanetary disk surrounding the T Tauri star TW Hydra by computing spectral energy distributions (SEDs) and comparing them to observed infrared fluxes. The emergent spectrum from the assumed passive disk is calculated using a "1.5-D" radiative transfer code. The vertical temperature distributions of several dust populations are solved for simultaneously in each annulus of the disk, and the emergent spectra from all annuli are summed to produce the SED. The moment equations are closed using the approach of variable Eddington factors, which we solve for using ray tracing. Our approach includes scattering.
Our calculations largely confirm the results of Chiang & Goldreich (1997), who attribute 10 um silicate emission features seen in protoplanetary disks to a superheated dust layer. Our computed SEDs provide a good fits to the 8-12 um observations of Weinberger et al (2002) provided the maximum radius of the dust grains in the superheated layer is 1.5 um, and the dust grains are mostly amorphous, Fe-rich silicates. We present upper limits on the abundance of crystalline silicates in the TW Hydra disk.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.