Monday

We present the results of an ongoing search for close stellar companions to transiting exoplanet systems in the Southern hemisphere. The presence of stellar companions to hot Jupiters can strongly affect their formation and evolution, and are a key part of some theories of hot Jupiter migration. Contaminating light can affect all measurements, but particularly affects transmission spectroscopy, which we have seen for WASP-103Ab. However, our recently published results for WASP-20AB, previously thought to be only a single star, have shown that even simple planet properties such as mass and radius can be drastically changed by the presence of a second star.