Five New Exoplanets Orbiting Three Metal-rich, Massive Stars: Two-planet Systems Including Long-period Planets and an Eccentric Planet

We report detections of new exoplanets from a radial-velocity (RV) survey of metal-rich FGK stars by using three telescopes. By optimizing our RV analysis method to long time-baseline observations, we have succeeded in detecting five new Jovian planets around three metal-rich stars, HD 1605, HD 1666, and HD 67087, with masses of 1.3 {{M}_⊙ }, 1.5 {{M}_⊙ }, and 1.4 {{M}_⊙ }, respectively. A K1 subgiant star, HD 1605 hosts two planetary companions with minimum masses of {{M}_p}sin i=0.96{{M}_Jup} and 3.5{{M}_Jup} in circular orbits with the planets’ periods P=577.9 and 2111 days, respectively. HD 1605 shows a significant linear trend in RVs. Such a system consisting of Jovian planets in circular orbits has rarely been found and thus HD 1605 should be an important example of a multi-planetary system that is likely unperturbed by planet-planet interactions. HD 1666 is an F7 main-sequence star that hosts an eccentric and massive planet of {{M}_p}sin i=6.4{{M}_Jup} in an orbit with {{a}_p}=0.94 AU and eccentricity e=0.63. Such an eccentric and massive planet can be explained as a result of planet-planet interactions among Jovian planets. While we have found large residuals of rms=35.6 m {{s}^-1}, the periodogram analysis does not support any additional periodicities. Finally, HD 67087 hosts two planets of {{M}_p}sin i=3.1{{M}_Jup} and 4.9{{M}_Jup} in orbits with P=352.2 and 2374 days, and e=0.17 and 0.76, respectively. Although the current RVs do not lead to accurate determinations of its orbit and mass, HD 67087 c can be one of the most eccentric planets ever discovered in multiple systems.