OGLE-2017-BLG-1522: A Giant Planet around a Brown Dwarf Located in the Galactic Bulge

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 <SUB>E</SUB> ˜ 7.5 days. The Einstein radius is unusually small, θ <SUB>E</SUB> = 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}<SUB>host</SUB>},{M}<SUB>planet</SUB>})=({46}<SUB>-25</SUB><SUP>+79</SUP>,{0.75}<SUB>-0.40</SUB><SUP>+1.26</SUP>) {M}<SUB>{{J</SUB>}} and source-lens distance {D}<SUB>LS</SUB>}={0.99}<SUB>-0.54</SUB><SUP>+0.91</SUP> {kpc}, 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<SUP>-1</SUP>. The projected companion-host separation is {0.59}<SUB>-0.11</SUB><SUP>+0.12</SUP> {au}, indicating that the planet is placed beyond the snow line of the host, i.e., a <SUB> sl </SUB> ˜ 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.