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Explaining millimeter-sized particles in brown dwarf disks

Pinilla, P. and Birnstiel, T. and Benisty, M. and Ricci, L. and Natta, A. and Dullemond, C. P. and Dominik, C. and Testi, L. (2013) Explaining millimeter-sized particles in brown dwarf disks. Astronomy and Astrophysics, 554 . Art. No. A95 . ISSN 0004-6361. doi:10.1051/0004-6361/201220875.

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Context. Planets have been detected around a variety of stars, including low-mass objects, such as brown dwarfs. However, such extreme cases are challenging for planet formation models. Recent sub-millimeter observations of disks around brown dwarf measured low spectral indices of the continuum emission that suggest that dust grains grow to mm-sizes even in these very low mass environments. Aims. To understand the first steps of planet formation in scaled-down versions of T-Tauri disks, we investigate the physical conditions that can theoretically explain the growth from interstellar dust to millimeter-sized grains in disks around brown dwarf. Methods. We modeled the evolution of dust particles under conditions of low-mass disks around brown dwarfs. We used coagulation, fragmentation, and disk-structure models to simulate the evolution of dust, with zero and non-zero radial drift. For the non-zero radial drift, we considered strong inhomogeneities in the gas surface density profile that mimic long-lived pressure bumps in the disk. We studied different scenarios that could lead to an agreement between theoretical models and the spectral slope found by millimeter observations. Results. We find that fragmentation is less likely and rapid inward drift is more significant for particles in brown dwarf disks than in T-Tauri disks. We present different scenarios that can nevertheless explain millimeter-sized grains. As an example, a model that combines the following parameters can fit the millimeter fluxes measured for brown dwarf disks: strong pressure inhomogeneities of ~40% of amplitude, a small radial extent ~15 AU, a moderate turbulence strength α_(turb) = 10^(-3), and average fragmentation velocities for ices v_f = 10 m s^(-1).

Item Type:Article
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URLURL TypeDescription DOIArticle Paper
Pinilla, P.0000-0001-8764-1780
Benisty, M.0000-0002-7695-7605
Testi, L.0000-0003-1859-3070
Additional Information:© 2013 ESO. Article published by EDP Sciences. Received 7 December 2012; Accepted 22 April 2013. Published online 10 June 2013. We thank the anonymous referee for his/her constructive report, which helped us to improve and clarify the main results of the paper. T. Birnstiel acknowledges support from NASA Origins of Solar Systems grant NNX12AJ04G. P. Pinilla acknowledges the CPU time for running simulations in bwGRiD, member of the German D-Grid initiative, funded by the Ministry for Education and Research (Bundesministerium für Bildung und Forschung) and the Ministry for Science, Research and Arts Baden-Wuerttemberg (Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg).
Funding AgencyGrant Number
Bundesministerium für Bildung und Forschung (BMBF)UNSPECIFIED
Ministerium für Wissenschaft, Forschung und Kunst Baden-WürttembergUNSPECIFIED
Subject Keywords:accretion, accretion disks; protoplanetary disks; circumstellar matter; brown dwarfs; planets and satellites: formation
Record Number:CaltechAUTHORS:20130814-084729186
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39907
Deposited By: Tony Diaz
Deposited On:16 Aug 2013 23:06
Last Modified:09 Nov 2021 23:47

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