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Published April 2007 | Published
Journal Article Open

On the circum(sub)stellar environment of brown dwarfs in Taurus

Abstract

Aims. We want to investigate whether brown dwarfs (BDs) form like stars or are ejected embryos. We study the presence of disks around BDs in the Taurus cloud, and discuss implications for substellar formation models. Methods. We use photometric measurements from the visible to the far infrared to determine the spectral energy distributions (SEDs) of Taurus BDs. Results. We use Spitzer color indices, Hα as an accretion indicator, and models fit to the SEDs in order to estimate physical parameters of the disks around these BDs. We study the spatial distribution of BDs with and without disks across the Taurus aggregates, and we find that BDs with and without disks are not distributed regularly across the Taurus cloud. Conclusions. We find that 48%±14% of Taurus BDs have a circumstellar disk signature, a ratio similar to recent results from previous authors in other regions. We fit the SEDs and find that none of the disks around BDs in Taurus can be fitted convincingly with a flaring index β = 0, indicating that heating by the central object is efficient and that the disks we observe retain a significant amount of gas. We find that BDs with disks are proportionally more numerous in the northern Taurus filament, possibly the youngest filament. We do not find such a clear segregation for classical T Tauri stars (CTTS) and weak-lined T Tauri stars (WTTS), suggesting that, in addition to the effects of evolution, any segregation effects could be related to the mass of the object. A by-product of our study is to propose a recalibration of the Barrado y Navascués & Martín (2003) accretion limit in the substellar domain. The global shape of the limit fits our data points if it is raised by a factor 1.25–1.30.

Additional Information

© ESO 2007. Received 28 July 2006. Accepted 18 December 2006. We thank Cathie Clarke and Anthony Whitworth for enlightening discussions about BD formation models, and an anonymous referee for a detailed report that helped clarify many points in our paper. This research has made use of the CDS database. F.M. thanks the "Center for long Wavelength Astrophysics" for supporting a visit at JPL. We thank the Programme National de Physique Stellaire (PNPS, CNRS/INSU, France) for financial support.

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August 19, 2023
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