Abstract

During planetary transit, stellar light is filtered through an exoplanet’s atmosphere, revealing the planet’s atmospheric properties through wavelength-dependent absorption features. An increasing number of transmission spectra have been observed to date, forming a key data set for constraining planetary atmospheric compositions. They and have also revealed that atmospheric aerosols in the form of clouds and hazes are a common feature in exoplanet atmospheres. Major advances have been made regarding the optimization of observation and analysis of ground-based data in this context, and ground-based facilities are becoming important players in studying exoplanets.

I will present CHEWIE (Clouds, Hazes and Elements vieWed on gIant Exoplanets), a survey of exoplanet transmission spectra with large ground-based facilities, primarily using FORS2 at the ESO VLT and GMOS at the Gemini telescope. I will give an overview on the survey and present recent results such as the first transmission spectrum of WASP -103b, one of the most massive (1.5 $M_J$) and hottest (2500 K) planets characterized so far through transmission spectroscopy.