Planets and brown dwarfs in close orbits will interact with their host stars, as soon as they evolve to become red giants. However, the outcome of those interactions is still unclear. Recently, several brown dwarfs have been discovered orbiting hot subdwarf stars (sdB) in very short orbital periods of 0.065 - 0.096 d. Those compact helium stars are the stripped cores of the red giant, which lost their envelopes due to the interaction with a close companion. More than 3% of those stars might have close substellar companions. This shows that such companions can significantly affect late stellar evolution and that sdB binaries are ideal objects to study this influence. Currently more than 30 eclipsing sdB binary systems with cool low-mass companions have been discovered. We are using this unique sample to derive the mass distribution of the companions, constrain the fraction of substellar companions and determine the minimum mass needed to strip the red-giant of its envelope. We are especially interested in testing models that predict hot Jupiter planets as possible companions.
Professors: Maja Vuckovic