Authors

Timothy Rodigas, Phil Hinz, Jared Males

Affiliations

Steward Observatory

Abstract

We show that the observed radial velocity (RV) exoplanet eccentricity distribution, which is problematically skewed towards e > 0.1, can be explained by two populations of exoplanets: one of two-planet systems where both planets have e = 0, and the other of single-planets that truly are eccentric. In the case of the two-planet systems, the wider companion is never detected, nor does a long-term trend appear, but the Keplerian-fitted eccentricity of the inner planet is slightly increased. We use this bias to then predict the fraction of known exoplanets that may have undetected outer companions. We find that planets with 0.1 < e < 0.3 have a 15-20% chance of having an undetected outer companion. Using this criterion, we have begun a direct imaging campaign of a select few RV stars with MMTAO/Clio. We report here our results for the 14 Her planetary system, which has one confirmed planet and a long-term trend. While we do not detect the outer planet, we set strong constraints on its mass and separation. Based on our results, the undetected companion is mostly likely a planet rather than a brown dwarf. The overlap between RV and direct imaging is important for fully characterizing a planetary system architecture and we encourage high-contrast imagers to target RV stars in favorable cases.