Oral title: Results from the CHEWIE survey of giant exoplanet atmospheres

Oral 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 latest results such as the first high-precision transmission spectrum of 
WASP-103b. WASP-103b, a planet which is at the brink of tidal disruption by its host star. It is one of the most massive 
(1.5 M_J) and hottest (2500 K) planets characterized so far through transmission spectroscopy. Using GMOS, we have 
detected strong absorption features of Na and K in the planet's atmosphere, pointing towards a low contribution from 
atmospheric aerosols. This property makes WASP-103b a benchmark target for further atmospheric studies and an ideal 
laboratory to study one of the most extreme planetary environments.