Twenty Years of Precise Radial Velocities at Keck and Lick Observatories

TL;DR

This paper reviews over 20 years of precise radial velocity measurements at Keck and other observatories, revealing new long-period exoplanets, their orbital characteristics, and the importance of combining multiple datasets for accurate detection.

Contribution

It presents new long-period giant planet solutions, highlights the benefits of combining datasets from multiple observatories, and discusses stellar activity effects on RV measurements.

Findings

Discovery of several long-period giant planets.

Identification of high period-ratio planet pairs.

Stellar activity cycles can mimic planetary signals.

Abstract

The precise radial velocity survey at Keck Observatory began over 20 years ago. Its survey of thousands of stars now has the time baseline to be sensitive to planets with decade-long orbits, including Jupiter analogs. I present several newly-finished orbital solutions for long-period giant planets. Although hot Jupiters are generally "lonely" (i.e. they are not part of multiplanet systems), those that are not appear to often have giant companions at 5 AU or beyond. I present two of the highest period- ratios among planets in a two-planet system, and some of the longest orbital periods ever measured for exoplanets. In many cases, combining Keck radial velocities from those from other long-term surveys at Lick Observatory, McDonald Observatory, HARPS, and, of course, OHP spectrographs, produces superior orbital fits, constraining both period and eccentricity better than could be possible with any single set alone. Stellar magnetic activity cycles can masquerade as long-period planets. In most cases this effect is very small, but a loud minority of stars, including, apparently, HD 154345, show very strong RV-activity correlations.