Myrla Phillippe

We present a grid of thermal emission contribution functions and their corresponding atmospheric spectra model for cloudy and cloud-free brown dwarfs, spanning effective temperatures T _eff ∈ [500, 2000][K], surface gravities log g = [ 3.5 , 5.5 ] [cgs], sedimentation efficiencies f _sed = 1, 2, 3, 4, and 8, and eddy diffusion coefficients log K zz = [ 6 , 11 ] . We use temperature–pressure profiles from the Sonora Diamondback models in conjunction with the picaso radiative transfer code and the cloud modeling code virga , to explore how different atmospheric parameters influence the vertical distribution of emitted radiation for atmospheres in chemical equilibrium. We confirm that cloud opacity significantly impacts atmospheric emission depth in prominent molecular features, such as CH ₄ , H ₂ O, CO, NH ₃ , CO ₂ , and atomic features Na and K. The atmospheric emission depth varies most notably in the J band, and at midresolution spectra in the Na and K doublets. Our analysis highlights pressure-wavelength differences between cloudy and cloud-free atmospheres for characterizing L, L/T transition, and T-type brown dwarfs and demonstrates how contribution functions can guide targeted spectroscopic investigations. To facilitate observational planning, we provide an accessible database and web-based application that enable the community to compare observational data with our model grid of spectra and contribution functions with a wavelength range of 0.5–30 μ m.

We present a new analysis of the spectroscopic variability of WISE J104915.57−531906.1AB (WISE 1049AB, L7.5+T0.5), observed using the NIRSpec instrument on board the James Webb Space Telescope (GO 2965; PI: Biller). We explore the variability of the dominant molecular bands present in their 0.6–5.3 μ m spectra (H ₂ O, CH ₄ , and CO), finding that the B component exhibits a higher maximum deviation than the A component in all the wavelength ranges tested. The light curves reveal wavelength-dependent (atmospheric depth) and possibly chemistry-dependent variability. In particular, for the A component, the variability in the light curves at the wavelengths traced by the CH ₄ and CO molecular absorption features is higher than that for of H ₂ O, even when both trace similar pressure levels. We conclude that clouds alone are unlikely to explain the increased variability of CO and CH ₄ with respect to H ₂ O, suggesting that an additional physical mechanism is needed to explain the observed variability. This mechanism is probably due to thermochemical instabilities. Finally, we provide visual representations of the 3D atmospheric maps reconstructed for both components using the molecular band contributions at different pressure levels and the fits of planetary-scale waves.