摘要：We report the discovery of a planet in the microlensing event OGLE-2018-BLG-1269 with a planet-host mass ratio 9 6 X 10 i.e.， 0.6 times maller than the Jupiter/Sun mass ratio. Combined with the Gaia parallax and proper motion, a strong one-dimensional constraint on the microlens parallax vector allows us to significantly reduce the uncertainties of lens physical parameters. A Bayesian analysis that ignores any information about light from the host elds that the lanet is a cold ant（M=0.6=M）orbit a Sulik a（ 3M）at aisan of DL=2. 56 kpe. The projected planet host separation is d =4. 611. au. Using Gaia astrometry, we show that the blended light lies 12 mas from the host and therefore must be either the host star or a stellar companion to the host. An isochrone analysis favors the former possibility at >99.6%. The host is therefore a subgiant. For host metallicities in the range of 0.0 【 Fe/H】<+0.3， the host and planet masses are then in the range of 1.16≤M/M。≤1.38and0.74≤M2/M」≤0.89， respectively. Low host metallicities are excluded. The brightness and proximity of the lens make the event a strong candidate for spectroscopic follow-up both to test the microlensing solution and to further characterize the system.
