Invited Talks

The observed chemical abundances of ultracool atmospheres represent the interplay of numerous closely coupled chemical and physical processes, including equilibrium chemistry, disequilibrium mixing, photochemistry, and condensate formation. With improved observations has come increased interest in the role of cloud formation: a process that both depletes condensable species from the gas phase and introduces particulate opacities that may strongly shape emergent spectra. However, the sequence and distribution of condensates, interactions between cloud condensates, potential dis-equilibrating processes, and the kinetics of cloud formation remain incompletely understood. In this talk we will briefly review the history of modeling the chemistry of substellar atmospheres, explore variations introduced by metallicity and element abundance ratios and their connections to formation and evolution pathways, and highlight key questions in our chemical understanding of substellar objects.

The circumstellar disks around young stars are the sites of planet formation, with the composition of the parent disk imprinted on the planets that form therein.  In recent years, observational facilities like ALMA and JWST have greatly advanced the study of protoplanetary disk chemistry and its connection to the ongoing physical/dynamical evolution accompanying planet formation.  In this talk, I will highlight our current understanding of the gas and ice compositions and distributions in disks, implications for observable signatures in giant planets, and outstanding questions for the years ahead.

JWST observations of substellar atmospheres from brown dwarfs to planets both near and far are revealing the importance of detailed carbon, sulfur, and oxygen chemistry for these worlds. Both photochemical and thermochemical processes profoundly influence these atmospheres, but require new laboratory ground-truth to be implemented into the models we use to interpret observational data. I will discuss the past few years of laboratory haze, cloud, and atmospheric evolution studies, haze formation, cloud condensation pathways and morphology, and their implications for warmer atmospheres. I will discuss recent work to obtain new optical properties of aerosols and how these compare to those most often used in the literature. Finally, I will outline the greatest needs for future laboratory work and observations that can bring us closer to understanding complex chemistry on diverse worlds

Brown dwarfs offer a powerful laboratory for studying atmospheric physics. Interpreting their observed properties requires models that connect observables to atmospheric structure in a physically self-consistent way. In this talk, I will survey the development and current state of self-consistent brown dwarf atmosphere models, with an emphasis on radiative–convective equilibrium frameworks. I will discuss how the latest models have moved beyond assumptions such as cloud-free atmospheres and thermochemical equilibrium toward improved opacities, treatments of disequilibrium chemistry, rainout chemistry, and increasingly sophisticated cloud treatments. I will highlight how clouds and disequilibrium chemistry can reshape atmospheric energy balance, altering temperature–pressure structures and emergent spectra. I will also review our current understanding of atmospheric dynamics in brown dwarfs, as well as the different treatments of convection adopted in substellar atmosphere models. I will briefly touch on how stellar irradiation can fundamentally alter the atmospheres of transiting brown dwarfs. Finally, I will outline key areas for future work and the challenges and opportunities they present.

Brown dwarfs are a link between stellar and planetary astrophysics. Their spectra contain important information on their fundamental properties that can be used to their reveal formation and evolutionary histories. Interpreting brown dwarf spectra requires careful modeling of their atmospheres. In this review talk, I will give an overview of modeling efforts for brown dwarfs with a focus on atmospheric retrievals. I will provide a crash course in how the atmospheric retrieval technique works and common assumptions included in our atmospheric models. I will also review key results from atmospheric retrieval studies across the LTY sequence and highlight the synergies between other modeling techniques and retrievals. Looking to the future, I will discuss open questions and outstanding challenges currently being tackled by the field.

Abstract: TBD