Name/Affiliation: Joe Llama (University of St Andrews)
Detecting Exoplanetary Magnetic Fields
Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System. Near-UV observations of the WASP-12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. A number of possible explanations have been suggested for this variation, including the presence of a magnetospheric bow shock arising from the interaction of the planet\'s magnetic field with the stellar wind from it\'s host star. Such observations provide the first method for directly detecting the presence of a magnetic field on exoplanets. The shape and size of such asymmetries is highly dependent on the structure of the host stars magnetic field at the time of observation. This implies we may observe highly varying near-UV transit light curves for the same system. These variations can then be used to learn about the geometry of the host star\'s magnetic field. For some systems, such as HD 189733, we have maps of the surface magnetic field of the star at various epochs. In this talk I will show how incorporating these maps into a stellar wind model, I can model the formation of a bow shock around the planet and hence demonstrate the variability of the near-UV transits.