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Abundant Crystalline Silicates in the Disk of a Very Low Mass Star

Merín, B. and Augereau, J.-C. and van Dishoeck, E. F. and Kessler-Silacci, J. and Dullemond, C. P. and Blake, G. A. and Lahuis, F. and Brown, J. M. and Geers, V. C. and Pontoppidan, K. M. and Comerón, F. and Frasca, A. and Guieu, S. and Alcalá, J. M. and Boogert, A. C. A. and Evans, N. J., II and D'Alessio, P. and Mundy, L. G. and Chapman, N. (2007) Abundant Crystalline Silicates in the Disk of a Very Low Mass Star. Astrophysical Journal, 661 (1). pp. 361-367. ISSN 0004-637X.

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We announce the discovery of SST-Lup3-1, a very low mass star close to the brown dwarf boundary in Lupus III with a circum(sub)stellar disk, discovered by the "Cores to Disks" Spitzer Legacy Program from mid-infrared, with very conspicuous crystalline silicate features in its spectrum. It is the first of such objects with a full 5-35 μm spectrum taken with the IRS, and it shows strong 10 and 20 μm silicate features with high feature-to-continuum ratios and clear crystalline features out to 33 μm. The dust in the disk upper layer has a crystalline silicate grain fraction between 15% and 33%, depending on the assumed dust continuum. The availability of the full Spitzer infrared spectrum allows an analysis of the dust composition as a function of temperature and position in the disk. The hot (~300 K) dust responsible for the 10 μm feature consists of a roughly equal mix of small (~0.1 μm) and large (~1.5 μm) grains, whereas the cold (~70 K) dust responsible for the longer wavelength silicate features contains primarily large grains (>1 μm). Since the cold dust emission arises from deeper layers in the inner (<3 AU) disk as well as from the surface layers of the outer (3-5 AU) disk, this provides direct evidence for combined grain growth and settling in the disk. The inferred crystalline mass fractions in the two components are comparable. Since only the inner 0.02 AU of the disk is warm enough to anneal the amorphous silicate grains, even the lowest fraction of 15% of crystalline material requires either very efficient mixing or other formation mechanisms.

Item Type:Article
Related URLs:
URLURL TypeDescription
van Dishoeck, E. F.0000-0001-7591-1907
Blake, G. A.0000-0003-0787-1610
Pontoppidan, K. M.0000-0001-7552-1562
Evans, N. J., II0000-0001-5175-1777
Additional Information:© 2007 The American Astronomical Society. Received 2006 September 21; accepted 2007 January 23. B. M. thanks the Fundacion Ramon Areces for financial support. The authors thank Michiel Min and Jeroen Bouwman for fruitful discussions on crystalline silicates, and the referee for a detailed report that improved the impact of the paper substantially. Support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided through contracts 1256316, 1224608, and 1230780, issued by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Astrochemistry at Leiden is supported by a NWO Spinoza and NOVA grant, and by the European Research Training Network ‘‘The Origin of Planetary Systems’’ (PLANETS, contract HPRNCT- 2002-00308).
Funding AgencyGrant Number
Fundación Ramón ArecesUNSPECIFIED
European Research Training NetworkHPRN-CT-2002-00308
Subject Keywords:circumstellar matter; stars : individual (SST-Lup3-1); stars : low-mass, brown dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:20100318-090726515
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17768
Deposited By: Tony Diaz
Deposited On:20 Mar 2010 03:51
Last Modified:09 Dec 2019 21:39

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