Astrophys. J., 831, 97-97 (2016/November-1)
Herschel-resolved outer belts of two-belt debris disks-evidence of icy grains.
MORALES F.Y., BRYDEN G., WERNER M.W. and STAPELFELDT K.R.
Abstract (from CDS):
We present dual-band Herschel/PACS imaging for 59 main-sequence stars with known warm dust (Twarm ∼ 200 K), characterized by Spitzer. Of 57 debris disks detected at Herschel wavelengths (70 and/or 100 and 160 µm), about half have spectral energy distributions (SEDs) that suggest two-ring disk architectures mirroring that of the asteroid-Kuiper Belt geometry; the rest are consistent with single belts of warm, asteroidal material. Herschel observations spatially resolve the outer/cold dust component around 14 A-type and 4 solar-type stars with two-belt systems, 15 of which for the first time. Resolved disks are typically observed with radii >100 AU, larger than expected from a simple blackbody fit. Despite the absence of narrow spectral features for ice, we find that the shape of the continuum, combined with resolved outer/cold dust locations, can help constrain the grain size distribution and hint at the dust's composition for each resolved system. Based on the combined Spitzer/IRS+Multiband Imaging Photometer (5-to-70 µm) and Herschel/PACS (70-to-160 µm) data set, and under the assumption of idealized spherical grains, we find that over half of resolved outer/cold belts are best fit with a mixed ice/rock composition. Minimum grain sizes are most often equal to the expected radiative blowout limit, regardless of composition. Three of four resolved systems around the solar-type stars, however, tend to have larger minimum grains compared to expectation from blowout (fMB = amin/aBOS ∼ 5). We also probe the disk architecture of 39 Herschel-unresolved systems by modeling their SEDs uniformly, and find them to be consistent with 31 single- and 8 two-belt debris systems.
© 2016. The American Astronomical Society. All rights reserved.
circumstellar matter - infrared: planetary systems - planets and satellites: formation - planets and satellites: formation
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