The CORALIE survey for southern extra-solar planets. XV. Discovery of two eccentric planets orbiting HD 4113 and HD 156846

We report the detection of two very eccentric planets orbiting HD 4113 and HD 156846 with the CORALIE Echelle spectrograph mounted on the 1.2-m Euler Swiss telescope at La Silla. The first planet, HD 4113 b, has minimum mass of m sin{i}=1.6 ± 0.2 M_Jup, a period of P=526.59 ± 0.21 days and an eccentricity of e=0.903 ± 0.02. It orbits a metal rich G5V star at a=1.28 AU, which displays an additional radial velocity drift of 28 m s^-1 yr^-1 observed during 8 years. The combination of the radial-velocity data and the non-detection of any main sequence stellar companion in our high contrast images, taken at the VLT with NACO/SDI, characterizes the companion as a probable brown dwarf or as a faint white dwarf. The second planet, HD 156846 b, has minimum mass of m sin{i}=10.45 ± 0.05 M_Jup, a period of P=359.51 ± 0.09 days, an eccentricity of e=0.847 ± 0.002 and is located at a=1.0 AU from its parent star. HD 156846 is a metal rich G0 dwarf and is also the primary of a wide binary system (a>250 AU, P>4000 years). Its stellar companion, IDS 17147-1914 B, is a M4 dwarf. The very high eccentricities of both planets can be explained by Kozai oscillations induced by the presence of a third object.