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

TL;DR

This study models a possible dusty ring around the young brown dwarf G196-3B to explain its red colors, suggesting a debris disc with specific properties that fits observed spectral data.

Contribution

It introduces a debris disc model around G196-3B, providing an alternative explanation for its red colors and matching spectral energy distribution observations.

Findings

Debris disc at 0.12-0.20 R_sun from G196-3B fits spectral data.

Disc composed of sub-micron/micron dust particles near sublimation temperature.

Model suggests a ring similar to planetary rings but hotter and thicker.

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 $\sim 15$ $M_{\rm Jup}$ 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 ($T_{\rm eff} \approx 1870$~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.