An ACCESS and LRG-BEASTS optical transmission spectrum of the ultra-hot Jupiter WASP-103b

Ultra-hot Jupiters (Teq > 2000K) are a fascinating class of exoplanet, with the temperatures of their upper atmospheres comparable to stellar atmospheres. It was initially predicted that these planets would show significant absorption from TiO and VO, however, recent theoretical studies suggest that these molecules are thermally dissociated in the hottest (> 2500K) planets, removing them as opacity sources, while H- and atomic metals like Fe instead contribute significantly to the opacity. I will present an optical transmission spectrum of the ultra-hot Jupiter (2500K) WASP-103b, which straddles the predicted boundary at which TiO and VO are predicted to thermally dissociate. By combining 7 new transits from the ACCESS and LRG-BEASTS surveys, in addition to a re-analysis of archival VLT and Gemini data, I will present the most precise optical transmission spectrum of WASP-103b to date, which will allow us to confidently determine the presence of TiO and VO.