Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets

TL;DR

This paper provides detailed molecular opacity data and tables of Rosseland and Planck mean opacities crucial for modeling ultracool dwarf and exoplanet atmospheres, emphasizing the impact of alkali elements on opacity calculations.

Contribution

It introduces new, comprehensive opacity tables incorporating alkali elements and pressure-induced absorption, based on updated chemical equilibrium models for ultracool dwarfs and exoplanets.

Findings

Alkali atomic opacity significantly increases mean opacities.

The provided tables are useful for atmosphere, interior, and evolution studies.

Opacity data assembled from public databases, laboratory data, and numerical calculations.

Abstract

Opacities and chemical abundance data are crucial ingredients of ultracool dwarf and extrasolar giant planet atmosphere models. We report here on the detailed sources of molecular opacity data employed by our group for this application. We also present tables of Rosseland and Planck mean opacities which are of use in some studies of the atmospheres, interiors, and evolution of planets and brown dwarfs. For the tables presented here we have included the opacities of important atomic and molecular species, including the alkali elements, pressure induced absorption by hydrogen, and other significant opacity sources but neglect opacity from condensates. We report for each species how we have assembled molecular line data from a combination of public databases, laboratory data that is not yet in the public databases, and our own numerical calculations. We combine these opacities with abundances computed from a chemical equilibrium model using recently revised solar abundances to compute mean opacities. The chemical equilibrium calculation accounts for the settling of condensates in a gravitational field, and is applicable to ultracool dwarf and extrasolar planetary atmospheres, but not circumstellar disks. We find that the inclusion of alkali atomic opacity substantially increases the mean opacities over those currently in the literature at densities relevant to the atmospheres and interiors of giant planets and brown dwarfs. We provide our opacity tables for public use and discuss their limitations.