Temperature-dependent molecular absorption cross sections for exoplanets and other atmospheres

TL;DR

This paper introduces a method to convert extensive molecular line lists into temperature-dependent absorption cross sections, facilitating atmospheric modeling of exoplanets with a web-based tool for easy access.

Contribution

It presents a novel procedure to generate and interpolate molecular absorption cross sections from line lists, simplifying radiative transfer modeling for exoplanet atmospheres.

Findings

Cross sections accurately represent spectroscopic features.

Web interface enables easy access to temperature-dependent data.

Method reduces computational complexity for atmospheric models.

Abstract

Exoplanets, and in particular hot ones such as hot Jupiters, require a very significant quantities of molecular spectroscopic data to model radiative transport in their atmospheres or to interpret their spectra. This data is commonly provided in the form of very extensive transition line lists. The size of these line lists is such that constructing a single model may require the consideration of several billion lines. We present a procedure to simplify this process based on the use of cross sections. Line lists for water, H$_3^+$, HCN /HNC and ammonia have been turned into cross sections on a fine enough grid to preserve their spectroscopic features. Cross sections are provided at a fixed range of temperatures and an interpolation procedure which can be used to generate cross sections at arbitrary temperatures is described. A web-based interface (www.exomol.com/xsec) has been developed to allow astronomers to download cross sections at specified temperatures and spectral resolution. Specific examples are presented for the key water molecule.