Sinking Silicates. I. Characterizing the Benchmark System Containing the T0 Brown Dwarf CWISEJ210640.16+250729.0 using JWST

In this study, we present the full (97.3% complete) 0.8–12.5 μ m spectral energy distribution (SED) of an L/T transition object, CWISE J210640.16+250729.0 (CW 2106), 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 (≈ −4.825 dex) of CW 2106, and obtain estimates of its mass ( M ≈ 50–62 M Jup ), radius ( R ≈ 0.83–0.87 R Jup ), effective temperature ( T eff ≈ 1213 K), and surface gravity ( log g ≈ 5.28 dex). We find the near-infrared (near-IR) spectrum (0.8–2.5 μ m) is best reproduced with cloudy atmospheric models while the mid-infrared (mid-IR) spectrum (5–12.5 μ 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 μ m silicate feature. Making use of the Mg/Si ratio of the primary, alongside thermochemical models, we predict the clouds in CW 2106 to be composed primarily of enstatite (MgSiO 3 ), removing ∼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.