14 Her: A Likely Case of Planet–Planet Scattering

Abstract

In this Letter, we measure the full orbital architecture of the two-planet system around the nearby K0 dwarf 14 Herculis. 14 Her (HD 145675, HIP 79248) is a middle-aged (4.6_(-1.3)^(+3.8) Gyr) K0 star with two eccentric giant planets identified in the literature from radial velocity (RV) variability and long-term trends. Using archival RV data from Keck/HIRES in concert with Gaia-Hipparcos acceleration in the proper motion vector for the star, we have disentangled the mass and inclination of the b planet to 9.1_(-1.1)^(+1.0) M_(Jup) and 32.7)_(-3.2)^(+5.3) degrees. Despite only partial phase coverage for the c planet's orbit, we are able to constrain its mass and orbital parameters as well to 6.9_(-1.0)^(+1.7) M_(Jup) and 101_(-33)^(+31) degrees. We find that coplanarity of the b and c orbits is strongly disfavored. Combined with the age of the system and the comparable masses of its planets, this suggests that planet–planet scattering may be responsible for the current configuration of the system.