A planet in a close eccentric binary system around a K giant star: Testing dynamical configurations and the evolution of planetary systems

Based on radial velocity (RV) data from our Lick Planet Search of G/K giant stars we report the discovery of an extrasolar planet in a circumstellar orbit around a K giant star in a close eccentric binary system. We perform a double Keplerian fit to our Lick RV measurements supplemented with RVs from SONG. This yields a minimum mass of 1 to 1.4 Jupiter masses for the planet and a semi-major axis of approximately 1 AU. Due to the very high eccentricity of the binary orbit, the companion and the planet come close to each other at every periastron passage of the stellar companion, yielding very complicated dynamics in the system. We search for stable solutions in order to determine the dynamical configuration of the system. Furthermore it is unclear at the moment how a system like this could have emerged to form a stable configuration. The formation process of the planet remains a mystery, as the stellar companion in its current orbit would have prevented the planet from forming. Therefore, the system must have experienced significant changes in its orbital configuration and challenges existing formation and evolution theories of planetary systems.

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