The SOPHIE search for northern extrasolar planets VI. Three new hot Jupiters in multi-planet extrasolar systems

We present high-precision radial-velocity measurements of three solar-type stars: HD 13908, HD 159243, and HIP 91258. The observations were made with the SOPHIE spectrograph at the 1.93 m telescope of the Observatoire de Haute-Provence (France). They show that these three bright stars host exoplanetary systems composed of at least two companions. HD 13908 b is a planet with a minimum mass of 0.865 +/- 0.035 M-Jup on a circular orbit with a period of 19.382 +/- 0.006 days. There is an outer massive companion in the system with a period of 931 +/- 17 days, e = 0.12 +/- 0.02, and a minimum mass of 5.13 +/- 0.25 M-Jup. The star HD 159243 also has two detected companions with respective masses, periods, and eccentricities of M-p= 1.13 +/- 0.05 and 1.9 +/- 0.13 M-Jup, P = 12.620 +/- 0.004 and 248.4 +/- 4.9 days, and e = 0.02 +/- 0.02 and 0.075 +/- 0.05. Finally, the star HIP 91258 has a planetary companion with a minimum mass of 1.068 +/- 0.038 M-Jup, an orbital period of 5.0505 +/- 0.0015 days, and a quadratic trend indicating an outer planetary or stellar companion that is as yet uncharacterized. The planet-hosting stars HD 13908, HD 159243, and HIP 91258 are main-sequence stars of spectral types F8V, G0V, and G5V, respectively, with moderate activity levels. HIP 91258 is slightly over-metallic, while the other two stars have solar-like metallicity. The three systems are discussed in the frame of formation and dynamical evolution models of systems composed of several giant planets.