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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358621.0, MPI für Astronomie / Publikationen_mpia
Deep Spitzer spectroscopy of the "Flying Saucer'' edge-on disk: large grains beyond 50 AU
Authors:Pontoppidan, K. M.; Stapelfeldt, K. R.; Blake, G. A.; van Dishoeck, E. F.; Dullemond, C. P.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:The Astrophysical Journal
Start Page:L111
End Page:L114
Audience:Not Specified
Abstract / Description:We present deep Spitzer IRS low-resolution (lambda/Deltalambda~100) 5-35 mum spectroscopy of the edge-on disk the ``Flying Saucer'' (2MASS J16281370-2431391) in the Ophiuchus molecular cloud. The SED exhibits the characteristic two-peak shape predicted for a circumstellar disk viewed very close to edge-on. The short-wavelength peak is entirely due to photons scattered off the surface of the disk, while the long-wavelength peak is due to thermal emission from the disk itself. The Spitzer spectrum represents the first spectroscopic detection of scattered light out to 15 mum from a bona fide, isolated edge-on disk around a T Tauri star. The depth and the wavelength of the mid-infrared ``valley'' of the SED give direct constraints on the size distribution of large grains in the disk. Using a 2D continuum radiative transfer model, we find that a significant amount of 5-10 mum-sized grains is required in the surface layers of the disk at radii of 50-300 AU. The detection of relatively large grains in the upper layers implies that vertical mixing is effective, since grain growth models predict that the grains would otherwise settle deep in the disk on short timescales. Additionally, we tentatively detect the 9.66 mum S(3) line of H2 and the 11.2 mum emission feature due to PAHs.
Free Keywords:Stars: Circumstellar Matter; Infrared: ISM; Stars: Planetary Systems: Protoplanetary Disks; stars: individual (2MASS J16281370-2431391); Stars: Pre-Main-Sequence
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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