Abstract DGP2026-14

High resolution ground-based transmission spectroscopy has the potential to detect individual spectral lines in exoplanet atmospheres, allowing for a more accurate picture of planet composition and evolution. Higher resolutions allow for the detection and analysis of narrow band features, revealing fingerprints of species with complex spectra in exoplanet atmospheres such as iron and magnesium.
Transmission spectra containing the atmospheric information must be cleaned of many effects, but one of the most confounding to species detection is the Rossiter-McLaughlin effect, whereby the planet’s passage over the projected rotating stellar disk blocks alternately blue and red-shifted stellar light. This leads to a characteristic artifact at the line cores with a shape and strength dependent on the relative geometry of the observed system. This effect is particularly strong for the Hot Jupiter HD 189733b and must be cleaned from the transmission spectrum in order to conclusively detect metallic species.
Here we attempt to detect metallic species, specifically Fe I, Fe II and Mg I, in the atmosphere of the well-studied exoplanet HD 189733b using high spectral resolution ground-based observations. An indication as to the presence of metallic species can be obtained by cross-correlating the data with template spectra for each species, after removing the Rossiter-McLaughlin effect via a transit model.
We find that our model can only remove the Rossiter-McLaughlin effect with specific values for either the stellar rotation velocity or planet radius, at which point the Rossiter-McLaughlin effect is removed to within the scatter of our data. The results indicate a likely non-detection of both Fe II and Mg I however, the cross-correlation-boosted signal still contains a residual contaminating feature so the presence of Fe I can not be entirely ruled out.