OGLE-2012-bLG-0950Lb: the First Planet Mass Measurement From Only Microlens Parallax and Lens Flux

We report the discovery of a microlensing planet OGLE-2012-BLG-0950Lb with a planet/host mass ratio Periapsis Approx. = 2 x10(exp. -4). A long term distortion detected in both MOA and OGLE light curve can be explained by themicrolens parallax due to the Earths orbital motion around the Sun. Although the finite source effect is not detected, we obtain the lens flux by the high resolution Keck AO observation. Combining the microlens parallax and the lens flux reveal the nature of the lens: a planet with mass of M(sub p) = 35(+17/-)M compared to Earth is orbiting around an M-dwarf with mass of M(sub host) = 0.56(+0.12/-0.16) M compared to the Sun with a planet-host projected separation of r1 = 2.7(+0.6/-0.7) au located at Luminosity Distance = 3.0(+0.8/-1.1) kpc from us. This is the first mass measurement from only microlens parallax and the lens flux without the finite source effect. In the coming space observation-era with Spitzer, K2, Euclid, and WFIRST, we expect many such events for which we will not be able to measure any finite source effect. This work demonstrates an ability of mass measurements in such events.