Does Brown Dwarf G196-3B Have Saturn-like Rings?

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

Authors:

Zakhozhay et al

Abstract:

The origin of the very red optical and infrared colours of intermediate-age (∼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 ∼15 MJup 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 μm corresponds to the combination of an unreddened L3 atmosphere (Teff≈1870~K) and a warm (≈ 1280 K), narrow (≈ 0.07 - 0.11 R⊙) debris disc located at very close distances (≈ 0.12 - 0.20 R⊙) 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 ≥7×10−10 M⊕ 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 (≈6×103 km). Our inferred debris disc model is able to reproduce G196-3B's spectral energy distribution to a satisfactory level of achievement.