Bayesian evidence for two companions orbiting HIP 5158

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 e(48) 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 (msin 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 +/- 0.31ms(-1). We also analysed a three-companion model, but found it to be e(8) times less probable than the two-companion model.