On the properties of discs around accreting brown dwarfs

Abstract

We present a grid of models of accreting brown dwarf systems with circumstellar discs. The calculations involve a self-consistent solution of both vertical hydrostatic and radiative equilibrium along with a sophisticated treatment of dust sublimation. We have simulated observations of the spectral energy distributions and several broad-band photometric systems. Analysis of the disc structures and simulated observations reveals a natural dichotomy in accretion rates, with and ≤-9 classed as extreme and typical accretors, respectively. Derivation of ages and masses from our simulated photometry using isochrones is demonstrated to be unreliable even for typical accretors. Although current brown dwarf disc candidate selection criteria have been shown to be largely reliable when applied to our model grid we suggest improved selection criteria in several colour indices. We show that as accretion rates increase brown dwarf disc systems are less likely to be correctly identified. This suggests that, within our grid, systems with higher accretion rates would be preferentially lost during brown dwarf target selection. We suggest that observations used to assert a relationship may contain an intrinsic selection bias. © 2010 The Authors. Journal compilation © 2010 RAS.