Radial velocity data of epsilon Cyg

The radial velocities of the long-period (~53 years) spectroscopic binary epsilon Cyg (HIP 102488) are found to exhibit additional variations with a much shorter period (~291 days).

This signature is not perfectly regular, as its period and amplitude seem to change over time. We intend to improve the orbital solution of the epsilon Cyg system, and attempt to identify the cause of the nearly periodic shorter period variations, which might be due to an additional substellar companion. We use precise radial velocity measurements of the K-giant star epsilon Cyg from Lick Observatory, in combination with a large set of RVs collected more recently with the SONG telescope, as well as archival data sets.