2018AJ....155..219J

We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of t_E ∼ 7.5 days. The Einstein radius is unusually small, θ_E = 0.065 mas, implying that the lens system either has very low mass or lies much closer to the microlensed source than the Sun, or both. A Bayesian analysis yields component masses (M_host,M_planet)=(46_–25⁺⁷⁹,0.75_–0.40^+1.26)M_J and source-lens distance D_LS=0.99_–0.54^+0.91kpc, implying that this is a brown-dwarf/Jupiter system that probably lies in the Galactic bulge, a location that is also consistent with the relatively low lens-source relative proper motion µ = 3.2 ± 0.5 mas yr^–1. The projected companion-host separation is 0.59_–0.11^+0.12au, indicating that the planet is placed beyond the snow line of the host, i.e., a_sl ∼ 0.12 au. Planet formation scenarios combined with the small companion-host mass ratio q ∼ 0.016 and separation suggest that the companion could be the first discovery of a giant planet that formed in a protoplanetary disk around a brown-dwarf host.