Program: GS-2011B-Q-45

The characterization of hot Jupiter atmospheres is an important step for understanding the nature, diversity and origins of these objects. When observed in transmission in the blue part of the visible, hot Jupiter atmospheres can exhibit strong high altitude absorbers, haze traces and photochemical products. These processes are currently poorly understood and remain unconstrained, yet they drive the energy budget of these planets. We propose to have a better empirical knowledge of hot Jupiter atmospheric chemistry by extending the sample of observed objects in order to conduct comparative exoplanetology studies. We will measure the transmission spectrum of two prototypes of hot Jupiters, CoRoT-1b and Wasp-4b, in the blue optical to reveal the absorption strength of possible chemical features. We will observe the two planets during transits with Gemini-S/GMOS using a recently proved technique for obtaining space-telescope quality exoplanet transit spectroscopy from the ground. Our objective is to obtain the planet atmospheric compositions and to test the presence or absence of hazes. Furthermore, the combination of the proposed transmission spectrum measurements with optical and NIR transmisson and emission observations will provide strong constraints on the overall physical properties of these planets.