Bayesian fitting of Taurus brown dwarf spectral energy distributions

Abstract

We present derived stellar and disc parameters for a sample of Taurus brown dwarfs both with and without evidence of an associated disc. These parameters have been derived using an online fitting tool (http://bd-server.astro.ex.ac.uk/), which includes a statistically robust derivation of uncertainties, an indication of pa- rameter degeneracies, and a complete treatment of the input photometric and spectroscopic observations. The observations of the Taurus members with indications of disc presence have been fitted using a grid of theoretical models including detailed treatments of physical processes accepted for higher mass stars, such as dust sublimation, and a simple treatment of the accretion flux. This grid of models has been designed to test the validity of the adopted physical mechanisms, but we have also constructed models using parameterisation, for example semi-empirical dust sublimation radii, for users solely interested in parameter derivation and the quality of the fit. The parameters derived for the naked and disc brown dwarf systems are largely consistent with literature observations. However, our inner disc edge locations are consistently closer to the star than previous results and we also derive elevated accretion rates over non-SED based accretion rate derivations. For inner edge locations we attribute these differences to the detailed modelling we have performed of the disc structure, particularly at the crucial inner edge where departures in geometry from the often adopted vertical wall due to dust sublimation (and therefore accretion flux) can compensate for temperature (and therefore distance) changes to the inner edge of the dust disc. In the case of the elevated derived accretion rates, in some cases, this may be caused by the intrinsic stellar luminosities of the targets exceeding that predicted by the isochrones we have adopted.

The paper contains 35 pages with 15 figures and 17 tables. Accepted for publication in MNRAS

References in corpus (16)

• UV excess measures of accretion onto young very low-mass stars and brown dwarfs
• Radiative transfer in very optically thick circumstellar disks
• Exploring brown dwarf disks: A 1.3 mm survey in Taurus
• A maximum likelihood method for fitting colour-magnitude diagrams
• Near and Mid-IR Photometry of the Pleiades, and a New List of Substellar Candidate Members
• Accretion Disks around Young Stars: Lifetimes, Disk Locking and Variability
• Fitting the young main-sequence; distances, ages and age spreads
• A Survey for New Members of Taurus with the Spitzer Space Telescope
• A Tale of Two Herbig Ae stars -MWC275 and AB Aurigae: Comprehensive Models for SED and Interferometry
• No wide spread of stellar ages in the Orion Nebula Cluster
• Empirical isochrones and relative ages for young stars, and the radiative-convective gap
• Disks around Brown Dwarfs in the Sigma Orionis Cluster
• Magnetocentrifugally Driven Flows from Young Stars and Disks. VI. Accretion with a Multipole Stellar Field
• Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf
• The $\dot{M}-M$ relationship in pre-main sequence stars
• Structural and compositional properties of brown dwarf disks: the case of 2MASS J04442713+2512164

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• What can the SEDs of first hydrostatic core candidates reveal about their nature?