Five Intermediate-Period Planets from the N2K Sample

Abstract

We report the detection of five Jovian-mass planets orbiting high-metallicity stars. Four of these stars were first observed as part of the N2K program, and exhibited low rms velocity scatter after three consecutive observations. However, follow-up observations over the last 3 years now reveal the presence of longer period planets with orbital periods ranging from 21 days to a few years. HD 11506 is a G0 V star with a planet of M sin i = 4.74 M_(Jup) in a 3.85 yr orbit. HD 17156 is a G0 V star with a 3.12 M_(Jup) planet in a 21.2 day orbit. The eccentricity of this orbit is 0.67, one of the highest known for a planet with a relatively short period. The orbital period for this planet places it in a region of parameter space where relatively few planets have been detected. HD 125612 is a G3 V star with a planet of M sin i = 3.5 M_(Jup) in a 1.4 yr orbit. HD 170469 is a G5 IV star with a planet of M sin i = 0.67 M_(Jup) in a 3.13 year orbit. HD 231701 is an F8 V star with planet of 1.08 M_(Jup) in a 142 day orbit. All of these stars have supersolar metallicity. Three of the five stars were observed photometrically, but showed no evidence of brightness variability. A transit search conducted for HD 17156 was negative, but covered only 25% of the search space, and so is not conclusive.