2019AJ....158..224K

We report the discovery of a gas-giant planet orbiting a low-mass host star in the microlensing event MOA-bin-29 that occurred in 2006. We find five degenerate solutions with the planet/host-star mass ratio of q ∼ 10^–2. The Einstein radius crossing time of all models are relatively short (∼4-7 days), which indicates that the mass of host star is likely low. The measured lens-source proper motion is 5-9 mas yr^–1 depending on the models. Since only finite source effects are detected, we conduct a Bayesian analysis in order to obtain the posterior probability distribution of the lens physical properties. As a result, we find the lens system is likely to be a gas-giant orbiting a brown dwarf or a very late M-dwarf in the Galactic bulge. The probability distributions of the physical parameters for the five degenerate models are consistent within the range of error. By combining these probability distributions, we conclude that the lens system is a gas giant with a mass of M_p=0.63_–0.39^+1.13 M_Jup orbiting a brown dwarf with a mass of M_h=0.06_–0.04^+0.11 M_☉ at a projected star-planet separation of r_⊥=0.53_–0.18^+0.89 au. The lens distance is D_L=6.89_–1.19^+1.19 kpc, i.e., likely within the Galactic bulge.