Optical transmission spectroscopy of hot Jupiter atmospheres

The field of exoplanet atmospheres has advanced rapidly in the 16 years since the detection of sodium in the atmosphere of HD209458b. Giant planets on short period orbits (`hot Jupiters') have been key to this progression, due to their relatively characterisable atmospheres. Optical transmission spectroscopy revealed the first detection of an exoplanet atmosphere and has continued to play a vital role in atmospheric characterisation. In this thesis I present optical transmission spectroscopy of three hot Jupiters and place these in context within the LRG-BEASTS transmission spectroscopy survey. My ground-based transmission spectrum of WASP-52b revealed the presence of clouds in the planet's atmosphere and evidence for stellar faculae on the host. This study demonstrated that HST precision could be achieved from the ground. I also present ground-based transmission spectroscopy of HAT-P-18b. My precise transmission spectrum was well fitted with a Rayleigh scattering slope at the equilibrium temperature of the planet. The absence of broad sodium and potassium absorption led me to conclude that a high altitude haze was present. Finally I present a transmission spectrum of WASP-80b. I found that a haze was likely present in this planet's atmosphere and my transmission spectrum was inconsistent with a previously claimed detection of pressure-broadened potassium. My results are in agreement with the emerging correlation that cooler planets are less likely to have clear atmospheres. However, this correlation is still tentative. The LRG-BEASTS survey will test this relation and help improve our understanding of the underlying physics driving the formation of clouds and hazes in exoplanet atmospheres