Letter to the Editor

The CORALIE survey for southern extra-solar planets

XV. Discovery of two eccentric planets orbiting HD 4113 and HD 156846

¹ Observatoire astronomique de l'Université de Genève, 51 Ch. des Maillettes, Sauverny, 1290 Versoix, Switzerland e-mail: Damien.Segransan@obs.unige.ch
² School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
³ Laboratoire d'Astrophysique de Grenoble, BP 53, 38041 Grenoble Cedex, France
⁴ European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile
⁵ Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal

Received: 26 September 2007
Accepted: 30 October 2007

Abstract

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 ± , a period of ± 0.21 days and an eccentricity of ± 0.02. It orbits a metal rich G5V star at 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 ± , a period of ± 0.09 days, an eccentricity of ± 0.002 and is located at AU from its parent star. HD 156846 is a metal rich G0 dwarf and is also the primary of a wide binary system ( AU, 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.