Cross-sections for heavy atmospheres: H2O continuum. (February 2022)

• Record Type: Journal Article
• Authors: Anisman, Lara O.; Chubb, Katy L.; Elsey, Jonathan; Al-Refaie, Ahmed; Changeat, Quentin; Yurchenko, Sergei N.; Tennyson, Jonathan; Tinetti, Giovanna
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 278(2022)
• Publication Date: 2022-02
• Subjects: Exoplanets -- Atmospheres -- Water vapor -- Opacities -- Continuum absorption -- Super-Earths -- Mini-Neptunes; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2021.108013
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: Challenge to decipher spectroscopic signals of small exoplanets. Launch of JWST & Ariel will provide reams of high-quality data. Necessary for cross-sections used to model water to be equally as robust. Incorporating water continuum induces detectable transit depth differences. Imperative to include this into water cross-section calculations. Abstract: Most of the exoplanets detected up to now transit in front of their host stars, allowing for the generation of transmission spectra; the study of exoplanet atmospheres relies heavily upon accurate analysis of these spectra. Recent discoveries mean that the study of atmospheric signals from low-mass, temperate worlds are becoming increasingly common. The observed transit depth in these planets is small and more difficult to analyze. Analysis of simulated transmission spectra for two small, temperate planets (GJ 1214 b and K2-18 b) is presented, giving evidence for significant differences in simulated transit depth when the water vapor continuum is accounted for when compared to models omitting it. These models use cross-sections from the CAVIAR lab experiment for the water self-continuum up to 10, 000 cm − 1 ; these cross-sections exhibit an inverse relationship with temperature, hence lower-temperature atmospheres are the most significantly impacted. Including the water continuum strongly affects transit depths, increasing values by up to 60 ppm, with the differences for both planets being detectable with the future space missions Ariel and JWST. It is imperative that models of exoplanet spectra move toward adaptive cross-sections, increasingly optimized for H 2 O-rich atmospheres. This necessitates including absorption contribution from the water vapor continuum into atmospheric simulations.