The Lick-Carnegie Survey: Four New Exoplanet Candidates

TL;DR

This paper reports new radial velocity data for five nearby stars, confirming some planetary candidates and refuting others, thereby contributing to the understanding of exoplanet systems.

Contribution

It provides new precise RV measurements for five stars, confirming some planetary companions and refuting a previously claimed third planet in HD 74156.

Findings

Confirmed planets around HD 31253, HD 218566, HD 177830, HD 99492, and HD 74156.

Refuted the existence of the 336-day planet in HD 74156.

Provided detailed orbital parameters for the candidate planets.

Abstract

We present new precise HIRES radial velocity (RV) data sets of five nearby stars obtained at Keck Observatory. HD 31253, HD 218566, HD 177830, HD 99492 and HD 74156 are host stars of spectral classes F through K and show radial velocity variations consistent with new or additional planetary companions in Keplerian motion. The orbital parameters of the candidate planets in the five planetary systems span minimum masses of M sin i = 27.43 M_{earth} to M sin i = 8.28 M_{jup}, periods of 17.05 to 4696.95 days and eccentricities ranging from circular to extremely eccentric (e ~ 0.63). The 5th star, HD 74156, was known to have both a 52-day and a 2500-day planet, and was claimed to also harbor a 3rd planet at 336d, in apparent support of the "Packed Planetary System" hypothesis. Our greatly expanded data set for HD 74156 provides strong confirmation of both the 52-day and 2500-d planets, but strongly contradicts the existence of a 336-day planet, and offers no significant evidence for any other planets in the system.