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OGLE-2018-BLG-1269Lb: A Jovian Planet with a Bright I=16 Host
• 정연길; Andrew P. Gould; 정선주; 외
• 2020-09-02
• ASTRONOMICAL JOURNAL 160 3 : 148-1~148-18
We report the discovery of a planet in the microlensing event OGLE-2018-BLG-1269 with a planet？host mass ratio q ~ 6 × 10？4, i.e., 0.6 times smaller 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 yields that the planet is a cold giant $({M}_{2}={0.69}_{-0.22}^{+0.44}\,{M}_{{\rm{J}}})$ orbiting a Sun-like star $({M}_{1}={1.13}_{-0.35}^{+0.72}\,{M}_{\odot })$ at a distance of ${D}_{{\rm{L}}}={2.56}_{-0.62}^{+0.92}\,\mathrm{kpc}$. The projected planet？host separation is ${a}_{\perp }={4.61}_{-1.17}^{+1.70}\,\mathrm{au}$. Using Gaia astrometry, we show that the blended light lies $\lesssim 12\,\mathrm{mas}$ 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 $0.0\leqslant [\mathrm{Fe}/{\rm{H}}]\leqslant +0.3$, the host and planet masses are then in the range of $1.16\leqslant {M}_{1}/{M}_{\odot }\leqslant 1.38$ and $0.74\leqslant {M}_{2}/{M}_{{\rm{J}}}\leqslant 0.89$, 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.