The California Planet Survey IV: A Planet Orbiting the Giant Star HD 145934 and Updates to Seven Systems with Long-Period Planets

TL;DR

This paper updates orbital parameters for seven stars with long-period planets using new radial velocity data, revealing new planets and system architectures, which enhances understanding of planetary system diversity and evolution.

Contribution

It provides refined orbital data for seven long-period planetary systems, including the discovery of a new planet and the identification of additional companions, improving the understanding of such systems.

Findings

Discovery of HD 145934 b, a 2 M_Jup planet with a 7.5-year orbit.

Identification of a linear trend in HD 66428 indicating an additional companion.

Confirmation of multi-planet systems and long-period planets around several stars.

Abstract

We present an update to seven stars with long-period planets or planetary candidates using new and archival radial velocities from Keck-HIRES and literature velocities from other telescopes. Our updated analysis better constrains orbital parameters for these planets, four of which are known multi-planet systems. HD 24040 b and HD 183263 c are super-Jupiters with circular orbits and periods longer than 8 yr. We present a previously unseen linear trend in the residuals of HD 66428 indicative on an additional planetary companion. We confirm that GJ 849 is a multi-planet system and find a good orbital solution for the c component: it is a $1 M_{\rm Jup}$ planet in a 15 yr orbit (the longest known for a planet orbiting an M dwarf). We update the HD 74156 double-planet system. We also announce the detection of HD 145934 b, a $2 M_{\rm Jup}$ planet in a 7.5 yr orbit around a giant star. Two of our stars, HD 187123 and HD 217107, at present host the only known examples of systems comprising a hot Jupiter and a planet with a well constrained period $> 5$ yr, and with no evidence of giant planets in between. Our enlargement and improvement of long-period planet parameters will aid future analysis of origins, diversity, and evolution of planetary systems.