2011MNRAS.416L.104F

We present results of a Bayesian analysis of radial velocity data for the star HIP 5158, confirming the presence of two companions and also constraining their orbital parameters. Assuming Keplerian orbits, the two-companion model is found to be e⁴⁸ times more probable than the one-planet model, although the orbital parameters of the second companion are only weakly constrained. The derived orbital periods are 345.6±2.0 and 9017.8±3180.7 d, respectively, and the corresponding eccentricities are 0.54±0.04 and 0.14±0.10. The limits on planetary mass (m sin i) and semimajor axis are (1.44±0.14M_J, 0.89±0.01 au) and (15.04±10.55M_J, 7.70±1.88 au), respectively. Owing to the large uncertainty on the mass of the second companion, we are unable to determine whether it is a planet or a brown dwarf. The remaining `noise' (stellar jitter) unaccounted for by the model is 2.28±0.31 m/s. We also analysed a three-companion model, but found it to be e⁸ times less probable than the two-companion model.