Structural and compositional properties of brown dwarf disks: the case of 2MASS J04442713+2512164

¹ Astronomy Department, University of California, Berkeley, CA 94720, USA e-mail: hbouy@astro.berkeley.edu
² Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38200 - La Laguna, Tenerife, Spain e-mail: bouy@iac.es
³ Laboratorio de Astrofísca Espacial y Física Fundamental (LAEFF-INTA), Apdo 50727, 28080 Madrid, Spain
⁴ Astrophysics Group, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK
⁵ Laboratoire d'Astrophysique de Grenoble, CNRS, Université Joseph Fourier, UMR 5571, BP 53, 38041 Grenoble Cedex 9, France
⁶ Services d'Astrophysique Saclay CEA, 91191 Gif-sur-Yvette, France
⁷ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁸ Grantecan S.A., C/ Vía Láctea s/n, 38200 - La Laguna, Tenerife, Spain
⁹ Spitzer Science Center, California Institute of Technology, Mail Code 314-6, 1200 East California Boulevard, Pasadena, CA 91125, USA

Received: 18 October 2007
Accepted: 25 March 2008

Abstract

Aims. To improve our understanding of substellar formation, we have performed a compositional and structural study of a brown dwarf disk.

Methods. We present the results of photometric, spectroscopic, and imaging observations of 2MASS J04442713+2512164, a young brown dwarf (M 7.25) member of the Taurus association. Our dataset, combined with results from the literature, provides a complete coverage of the spectral energy distribution from the optical range to the millimeter, including the first photometric measurement of a brown dwarf disk at 3.7 mm, and allows us to perform a detailed analysis of the disk properties.

Results. The target was known to have a disk. High-resolution optical spectroscopy shows that it is accreting intensely, and powers both a jet and an outflow. The disk structure is similar to what is observed for more massive TTauri stars. Spectral decomposition models of Spitzer/IRS spectra suggest that the mid-infrared emission from the optically thin disk layers is dominated by grains with intermediate sizes (1.5 μm). Crystalline silicates are significantly more abundant in the outer part and/or deeper layers of the disk, implying very efficient mixing and/or additional annealing processes. Submillimeter and millimeter data indicate that most of the disk mass is in large grains (>1 mm).