Probing the atmosphere of HD189733b with the Na I and K I lines

TL;DR

This study uses high-resolution transmission spectroscopy to analyze the atmospheres of HD189733b, focusing on the sodium and potassium lines to understand atmospheric composition and dynamics.

Contribution

It provides the first resolved potassium absorption line profile for HD189733b and compares it with sodium lines and synthetic models to explore atmospheric properties.

Findings

Na I-D lines show broadening of about 10 km/s

K I line exhibits narrower broadening of a few km/s

Differences suggest varying atmospheric regions or low potassium abundance

Abstract

High spectral resolution transmission spectroscopy is a powerful tool to characterize exoplanet atmospheres. Especially for hot Jupiters, this technique is highly relevant, due to their high altitude absorption e.g. from resonant sodium (Na I) and potassium (K I) lines. We resolve the atmospheric K I-absorption on HD189733b with the aim to compare the resolved K I -line and previously obtained high resolution Na I-D-line observations with synthetic transmission spectra. The line profiles suggest atmospheric processes leading to a line broadening of the order of 10 km/s for the Na I-D-lines, and only a few km/s for the K I-line. The investigation hints that either the atmosphere of HD189733b lacks a significant amount of K I or the alkali lines probe different atmospheric regions with different temperature, which could explain the differences we see in the resolved absorption lines.