Sinking Silicates I: Characterizing the benchmark system containing the T0 brown dwarf CWISE J210640.16+250729.0 using JWST

Abstract

In this study, we present the full (97.3\% complete) 0.8--12.5 $\mu$m spectral energy distribution (SED) of an L/T transition object, CWISE J210640.16+250729.0 (CW2106), using the James Webb Space Telescope (JWST). We provide a full characterization of the host star's elemental abundances and age. We empirically derive the bolometric luminosity ($L_{\mathrm{bol}}\approx -4.825$ ${\text{L}}_{\odot }$) of CW2106, and obtain estimates of its mass (M$\approx 50-62$ M${}_{\mathrm{Jup}}$), radius (R$\approx 0.83-0.87$ R${}_{\mathrm{Jup}}$), effective temperature ($T_{\mathrm{eff}}$$\approx 1213$ K), and surface gravity ($\log g$$\approx 5.28$ dex). We find the near-infrared (near-IR) spectrum ($0.8-2.5\mu$m) is best reproduced with cloudy atmospheric models while the mid-infrared (mid-IR) spectrum ($5-12.5\mu$m) is best reproduced with cloudless models. This suggests a cloud layer restricted to only the deepest observable parts of the atmosphere and is qualified by the lack of a 9 $\mu$m silicate feature. Making use of the Mg/Si ratio of the primary, alongside thermochemical models, we predict the clouds in CW2106 to be composed primarily of enstatite (MgSiO${}_3$), removing $\sim 23\%$ of the bulk oxygen out of the atmosphere. Future retrieval studies will be able to help investigate the existence and full impact of these cloud species.

30 pages, 12 Figures, 4 Tables. Accepted for publication in ApJ