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

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 $1.3M_{\odot }$, $1.5M_{\odot }$, and $1.4M_{\odot }$, respectively. A K1 subgiant star HD 1605 hosts two planetary companions with the minimum masses of $M_p\sin i=0.96M_{\mathrm{JUP}}$ and $3.5M_{\mathrm{JUP}}$ 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 $M_p\sin i=6.4M_{\mathrm{JUP}}$ in the orbit with $a_{\mathrm{p}}=0.94$ 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 $\mathrm{rms}=35.6\mathrm{m}{\mathrm{s}}^{-1}$, the periodogram analysis does not support any additional periodicities. Finally, HD 67087 hosts two planets of $M_p\sin i=3.1M_{\mathrm{JUP}}$ and $4.9M_{\mathrm{JUP}}$ 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.

22 pages, 8 figures, accepted for publication in ApJ

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