Chiang, E. I. and Joung, M. K. and Creech-Eakman, M. J. and Qi, C. and Kessler, J. E. and Blake, G. A. and van Dishoeck, E. F. (2001) Spectral Energy Distributions of Passive T Tauri and Herbig Ae Disks: Grain Mineralogy, Parameter Dependences, and Comparison with Infrared Space Observatory LWS Observations. Astrophysical Journal, 547 (2). pp. 1077-1089. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20120914-142619288
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We improve upon the radiative, hydrostatic equilibrium models of passive circumstellar disks constructed by Chiang & Goldreich. New features include (1) an account for a range of particle sizes, (2) employment of laboratory-based optical constants of representative grain materials, and (3) numerical solution of the equations of radiative and hydrostatic equilibrium within the original two-layer (disk surface plus disk interior) approximation. We systematically explore how the spectral energy distribution (SED) of a face-on disk depends on grain size distributions, disk geometries and surface densities, and stellar photospheric temperatures. Observed SEDs of three Herbig Ae and two T Tauri stars, including spectra from the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO), are fitted with our models. Silicate emission bands from optically thin, superheated disk surface layers appear in nearly all systems. Water ice emission bands appear in LWS spectra of two of the coolest stars. Infrared excesses in several sources are consistent with significant vertical settling of photospheric grains. While this work furnishes further evidence that passive reprocessing of starlight by flared disks adequately explains the origin of infrared-to-millimeter wavelength excesses of young stars, we emphasize by explicit calculations how the SED alone does not provide sufficient information to constrain particle sizes and disk masses uniquely.
|Additional Information:||© 2001 American Astronomical Society. Received 2000 August 1; accepted 2000 September 21. We thank Cornelia Jäger and Ted Roush for providing optical constants of olivine and iron, respectively; Bruce Draine for suggesting that thermal spiking of PAHs might be responsible for observed near-infrared excesses; Jeroen Bouwman and Rens Waters for sending preprints of their work; Willem Schutte and Peter Goldreich for helpful discussions; and Antonella Natta for a useful referee's report. Support for E. I. C. and M. K. J. was provided by NASA grant NAG 5-7008. Additional support for E. I. C. was provided by NASA through a Hubble Fellowship grant awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. M. C. E. and G. A. B. acknowledge support through the NASA Origins and ISO block grant programs. J. E. K. is supported in part by a NASA GSRP fellowship. E. F. vD. acknowledges NWO grant 614.41.003.|
|Subject Keywords:||accretion, accretion disks; circumstellar matter; radiative transfer; stars: individual (MWC 480, HD 36112, CQ Tauri, LkCa 15, AA Tauri); stars: pre-main sequence|
|Official Citation:||Spectral Energy Distributions of Passive T Tauri and Herbig Ae Disks: Grain Mineralogy, Parameter Dependences, and Comparison with Infrared Space Observatory LWS Observations E. I. Chiang et al. 2001 ApJ 547 1077|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||14 Sep 2012 21:45|
|Last Modified:||26 Dec 2012 16:10|
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