Five Gas Giants Orbiting Metal Rich Stars

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

Authors:

Harakawa et al

Abstract:

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 the masses of 1.3M⊙, 1.5M⊙, and 1.4M⊙, respectively. A K1 subgiant star HD 1605 hosts two planetary companions with the minimum masses of Mpsini=0.96MJUP and 3.5MJUP in circular orbits with the planets' periods P=577.9 days 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 a F7 main sequence star which hosts an eccentric and massive planet of Mpsini=6.4MJUP in the orbit with ap=0.94 AU and an 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 the 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 Mpsini=3.1MJUP and 4.9MJUP in orbits with P=352.2 days 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.