The Janus head of the HD 12661 planetary system

In this work, we perform a global analysis of the radial velocity curve of the HD 12661 system. Orbital fits that are obtained by the genetic and gradient algorithms of minimization reveal the proximity of the system to the 6 : 1 mean motion resonance. The orbits are locked in the secular resonance with apsidal axes librating about 180degrees, with a full amplitude of similar or equal to90degrees-180degrees. Our solution incorporates the mutual interaction between the companions. A stability analysis with the MEGNO ( Mean Exponential Growth factor of Nearby Orbits) indicator shows that the system is located in an extended stable zone of quasi-periodic motions. These results are different from those obtained on the basis of the orbital fit published by Fischer et al.