Predicting Cloud Conditions in Substellar Mass Objects Using Ultracool Dwarf Companions

TL;DR

This study uses chemical analysis of benchmark brown dwarf companions to predict atmospheric composition and cloud formation, providing insights into brown dwarf chemistry and condensate processes relevant for future atmospheric modeling.

Contribution

It offers the first comprehensive chemical analysis of benchmark brown dwarf systems, predicting oxygen sinks and cloud formation sequences based on stellar and atmospheric data.

Findings

Median brown dwarf oxygen sink of 17.8% predicted.

Silicate cloud formation depends on Mg/Si ratio.

Implications for C/O ratio trends in substellar objects.

Abstract

We present results from conducting a theoretical chemical analysis of a sample of benchmark companion brown dwarfs whose primary star is of type F, G or K. We summarize the entire known sample of these types of companion systems, termed "compositional benchmarks", that are present in the literature or recently published as key systems of study in order to best understand brown dwarf chemistry and condensate formation. Via mass balance and stoichiometric calculations, we predict a median brown dwarf atmospheric oxygen sink of $17.8^{+1.7}_{-2.3}\%$ by utilizing published stellar abundances in the local solar neighborhood. Additionally, we predict a silicate condensation sequence such that atmospheres with bulk Mg/Si $\lesssim$ 0.9 will form enstatite (MgSiO$_3$) and quartz (SiO$_2$) clouds and atmospheres with bulk Mg/Si $\gtrsim$ 0.9 will form enstatite and forsterite (Mg$_2$SiO$_4$) clouds. Implications of these results on C/O ratio trends in substellar mass objects and utility of these predictions in future modeling work are discussed.