Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems

TL;DR

This paper updates orbital data for ten multi-planet systems, confirms some planets, revises others, and analyzes a catalog of 28 systems to reveal patterns in planetary system architectures and correlations with stellar properties.

Contribution

It provides new orbital fits for ten systems, confirms tentative planets, revises outer planet orbits, and compiles a catalog revealing statistical patterns in multi-planet systems.

Findings

At least 28% of known systems contain multiple planets.

Multi-planet systems have smaller eccentricities than single-planet systems.

Distribution of orbital distances differs between single and multi-planet systems.

Abstract

We present the latest velocities for 10 multi-planet systems, including a re-analysis of archival Keck and Lick data, resulting in improved velocities that supersede our previously published measurements. We derive updated orbital fits for ten Lick and Keck systems, including two systems (HD 11964, HD 183263) for which we provide confirmation of second planets only tentatively identified elsewhere, and two others (HD 187123, and HD 217107) for which we provide a major revision of the outer planet's orbit. We compile orbital elements from the literature to generate a catalog of the 28 published multiple-planet systems around stars within 200 pc. From this catalog we find several intriguing patterns emerging: - Including those systems with long-term radial velocity trends, at least 28% of known planetary systems appear to contain multiple planets. - Planets in multiple-planet systems have somewhat smaller eccentricities than single planets. - The distribution of orbital distances of planets in multi-planet systems and single planets are inconsistent: single-planet systems show a pile-up at P ~ 3 days and a jump near 1 AU, while multi-planet systems show a more uniform distribution in log-period. In addition, among all planetary systems we find: - There may be an emerging, positive correlation between stellar mass and giant-planet semi-major axis. - Exoplanets more massive than Jupiter have eccentricities broadly distributed across 0 < e < 0.5, while lower-mass exoplanets exhibit a distribution peaked near e = 0.