Consistent simulations of substellar atmospheres and non-equilibrium dust-cloud formation

TL;DR

This paper presents a novel approach integrating detailed cloud formation models with radiative transfer calculations to simulate substellar atmospheres, revealing significant differences from previous models and implications for temperature estimates.

Contribution

It introduces the first stellar atmosphere simulation based on actual cloud formation processes, combining non-equilibrium cloud modeling with a general-purpose atmosphere code.

Findings

Calculated (T,p) profiles differ from previous models DUSTY and COND.

Estimated effective temperature for a binary system is up to 500K higher than prior estimates.

Produced transition spectra and photometric fluxes for gas-giant planets with dust clouds.

Abstract

We aim to understand cloud formation in substellar objects. We combined the non-equilibrium, stationary cloud model of Helling, Woitke & Thi (2008; seed formation, growth, evaporation, gravitational settling, element conservation) with the general-purpose model atmosphere code PHOENIX (radiative transfer, hydrostatic equilibrium, mixing length theory, chemical equilibrium) in order to consistently calculate cloud formation and radiative transfer with their feedback on convection and gas phase depletion. We calculate the complete 1D model atmosphere structure and the chemical details of the cloud layers. The DRIFT-PHOENIX models enable the first stellar atmosphere simulation that is based on the actual cloud formation process. The resulting (T,p) profiles differ considerably from the previous limiting PHOENIX cases DUSTY and COND. A tentative comparison with observations demonstrates that the determination of effective temperatures based on simple cloud models has to be applied with care. Based on our new models, we suggest a mean Teff=1800K for the L-dwarf twin-binary system DENIS J0205-1159 which is up to 500K hotter than suggested in the literature. We show transition spectra for gas-giant planets which form dust clouds in their atmospheres and evaluate photometric fluxes for a WASP-1 type system.