Spitzer as a Microlens Parallax Satellite: Mass Measurement for the OGLE-2014-BLG-0124L Planet and its Host Star

We combine Spitzer and ground-based observations to measure the microlens parallax vector {\boldsymbol {π }}_E, and thus the mass and distance of OGLE-2014-BLG-0124L, making it the first microlensing planetary system with a space-based parallax measurement. The planet and star have masses of m ~ 0.5 M _jup and M ~ 0.7 M _⊙ and are separated by a ~ 3.1 AU in projection. The main source of uncertainty in all of these numbers (approximately 30%, 30%, and 20%) is the relatively poor measurement of the Einstein radius θ_E, rather than uncertainty in π_E, which is measured with 2.5% precision. This compares to 22% based on OGLE data alone, implying that the Spitzer data provide not only a substantial improvement in the precision of the π_E measurement, but also the first independent test of a ground-based {\boldsymbol {π }}_E measurement.