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Published September 2010 | Published
Journal Article Open

Structure and Composition of Two Transitional Circumstellar Disks in Corona Australis


The late stages of evolution of the primordial circumstellar disks surrounding young stars are poorly understood, yet vital to constraining theories of planet formation. We consider basic structural models for the disks around two ~10 Myr old members of the nearby RCrA association: RX J1842.9–3532 and RX J1852.3–3700. We present new arcsecond-resolution maps of their 230 GHz continuum emission from the Submillimeter Array and unresolved CO(3-2) spectra from the Atacama Submillimeter Telescope Experiment. By combining these data with broadband fluxes from the literature and infrared fluxes and spectra from the catalog of the Formation and Evolution of Planetary Systems Legacy program on the Spitzer Space Telescope, we assemble a multiwavelength data set probing the gas and dust disks. Using the Monte Carlo radiative transfer code RADMC to model simultaneously the spectral energy distribution and millimeter continuum visibilities, we derive basic dust disk properties and identify an inner cavity of radius 16 AU in the disk around RX J1852.3–3700. We also identify an optically thin 5 AU cavity in the disk around RX J1842.9–3532, with a small amount of optically thick material close to the star. The molecular line observations suggest an intermediate disk inclination in RX J1842.9–3532, consistent with the continuum emission. In combination with the dust models, the molecular data allow us to derive a lower CO content than expected, suggesting that the process of gas clearing is likely underway in both systems, perhaps simultaneously with planet formation.

Additional Information

© 2010 American Astronomical Society. Received 2010 February 27; accepted 2010 July 18; published 2010 August 13. We thank C. P. Dullemond for access to the two-dimensional version of RADMC. Partial support for this work was provided by NASA Origins of Solar Systems Program Grant NAG5-11777. A.M.H. acknowledges support from a National Science Foundation Graduate Research Fellowship. Support for S.M.A. was provided by NASA through Hubble Fellowship grant HF-01203-A 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.R.M. acknowledges the Harvard Origins of Life Initiative, the Smithsonian Astrophysical Observatory, and a NASA TPF Foundation Science Program grant NNG06GH25G (PI: S. Kenyon) for sabbatical support.

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