Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G196-3B

Abstract

The origin of the very red optical and infrared colours of intermediate-age ($\sim$10 - 500 Myr) L-type dwarfs remains unknown. It has been suggested that low-gravity atmospheres containing large amounts of dust may account for the observed reddish nature. We explored an alternative scenario by simulating protoplanetary and debris discs around G196-3B, which is an L3 young brown dwarf with a mass of $\sim 15$ $M_{\mathrm{Jup}}$ and an age in the interval 20 - 300 Myr. The best-fit solution to G196-3B's photometric spectral energy distribution from optical wavelengths through 24 $\mu$m corresponds to the combination of an unreddened L3 atmosphere ($T_{\mathrm{eff}}\approx 1870$~K) and a warm ($\approx$ 1280 K), narrow ($\approx$ 0.07 - 0.11 R${}_{\odot }$) debris disc located at very close distances ($\approx$ 0.12 - 0.20 R${}_{\odot }$) from the central brown dwarf. This putative, optically thick, dusty belt, whose presence is compatible with the relatively young system age, would have a mass $\ge 7\times 10^{-10}$ M${}_{\oplus }$ comprised of sub-micron/micron characteristic dusty particles with temperatures close to the sublimation threshold of silicates. Considering the derived global properties of the belt and the disc-to-brown dwarf mass ratio, the dusty ring around G196-3B may resemble the rings of Neptune and Jupiter, except for its high temperature and thick vertical height ($\approx 6\times 10^3$ km). Our inferred debris disc model is able to reproduce G196-3B's spectral energy distribution to a satisfactory level of achievement.

12 pages, 7 figures, 4 tables, accepted for publication in MNRAS

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• Radio emission in a nearby ultracool dwarf binary: a multi-frequency study
• New constraints on the presence of debris disks around G 196-3 B and VHS J125601.92-125723.9 b