A High Eccentricity Component in the Double Planet System Around HD 163607 and a Planet Around HD 164509

Abstract

We report the detection of three new exoplanets from Keck Observatory. HD 163607 is a metal-rich G5IV star with two planets. The inner planet has an observed orbital period of 75.29 $\pm$ 0.02 days, a semi-amplitude of 51.1 $\pm$ 1.4 \ms, an eccentricity of 0.73 $\pm$ 0.02 and a derived minimum mass of \msini = 0.77 $\pm$ 0.02 \mjup. This is the largest eccentricity of any known planet in a multi-planet system. The argument of periastron passage is 78.7 $\pm$ 2.0$^{\circ}$; consequently, the planet's closest approach to its parent star is very near the line of sight, leading to a relatively high transit probability of 8%. The outer planet has an orbital period of 3.60 $\pm$ 0.02 years, an orbital eccentricity of 0.12 $\pm$ 0.06 and a semi-amplitude of 40.4 $\pm$ 1.3 \ms. The minimum mass is \msini = 2.29 $\pm$ 0.16 \mjup. HD 164509 is a metal-rich G5V star with a planet in an orbital period of 282.4 $\pm$ 3.8 days and an eccentricity of 0.26 $\pm$ 0.14. The semi-amplitude of 14.2 $\pm$ 2.7 \ms\ implies a minimum mass of 0.48 $\pm$ 0.09 \mjup. The radial velocities of HD 164509 also exhibit a residual linear trend of -5.1 $\pm$ 0.7 \ms\ per year, indicating the presence of an additional longer period companion in the system. Photometric observations demonstrate that HD 163607 and HD 164509 are constant in brightness to sub-millimag levels on their radial velocity periods. This provides strong support for planetary reflex motion as the cause of the radial velocity variations.