Cloud Base Signature in Transmission Spectra of Exoplanet Atmospheres

TL;DR

This paper introduces an analytical model demonstrating how cloud bases in exoplanet atmospheres can create detectable features in transmission spectra, aiding in atmospheric characterization.

Contribution

The paper presents a new analytical model linking cloud bases to spectral inflections, enabling better interpretation of exoplanet transmission spectra.

Findings

Cloud bases produce observable inflection points in spectra

Inflections help determine cloud species and atmospheric conditions

Model applied successfully to HD 189733b data

Abstract

We present an analytical model for the transmission spectrum of a transiting exoplanet, showing that a cloud base can produce an observable inflection point in the spectrum. The wavelength and magnitude of the inflection can be used to break the degeneracy between the atmospheric pressure and the abundance of the main cloud material, however, the abundance still depends on cloud particle size. An observed inflection also provides a specific point on the atmospheric P-T profile, giving us a "thermometer" to directly validate or rule out postulated cloud species. We apply the model to the transit spectrum of HD 189733b.