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Wednesday 17 Sep 2014Photochemistry of hot exoplanets: modelling and experiments

Olivia Venot - Katholieke Universiteit Leuven, Instituut voor Sterrenkunde

Physics, 4th floor 14:00-15:00

To study hot exoplanets atmospheres, we have developed a chemical scheme adapted to their extreme temperatures and pressures. This scheme, made to described the kinetic of species with up to 2 carbon atoms, has been constructed in collaboration with specialist of combustion and has been validated against experiments. Thanks to this chemical network, we have studied the atmospheric composition of two warm Neptunes, GJ 3470b and GJ 436b, and in particular the influence of different parameters, like temperature, vertical mixing, UV flux, metallicity and tidal forces. I will show you that the CO/CH4 ratio of these planets depends on these parameters. But atmospheres with a high C/O ratio (equal or above 1) are enriched in heavy hydrocarbons and this C2 scheme may not be sufficient. That is why we have implemented another scheme, validated also against experiments, allowing to study species with up to 6 carbon atoms. I will present you this totally new chemical scheme.
Finally, I will show you experimental measurements that has been performed at high temperature to determine the absorption cross section of CO2 at temperatures relevant for warm exoplanets.

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