Exoplanets Orbiting G and K Giant Stars

Abstract

From a long-term RV survey of G and K giant stars at Lick Observatory we have identified, among others, a number of systems which most likely harbor at least one substellar companion. We have observed 16 of those systems with SONG in order to better constrain the periods of the outer companions, which often seem to be of the order of 20-50 years, as well as to understand the dynamical interaction between the components. Taken together the Lick and SONG data span 19 years. Here we report about a highly eccentric (e~0.93) stellar binary system that shows strong indications of a Jupiter mass planet orbiting the evolved primary component. Although the period of the stellar binary is 55 years, its orbit is very well determined due to the dense sampling by SONG during its recent periastron passage. If the planetary companion is confirmed, the system would be one of the closest and most eccentric stellar binaries known to host a planet, and it would raise questions how this planet could possibly have formed.