The influence of stellar chromospheres on exoplanet transmission spectroscopy

In the past years, enormous progress has been made in the field of exoplanet transmission spectroscopy. New techniques and instruments like the JWST now enable the determination of the properties of planetary atmospheres, as well as the detection of molecular species. In order to search for life on other planets via the minute signatures of biomarkers, we need to make sure that as many potential sources of systematic bias as possible are accounted for in the transit model.

However, in all approaches to this day, the stellar "background source" is viewed as a homogeneous disk consisting of only a photosphere.

In my presentation, I will first show that this assumption introduces strong biases in the derived transmission spectra and then introduce TACHELES, the first transit model that incorporates both a stellar photosphere and a chromosphere.