MagAO Observations of the Binary Microlens OGLE-2014-BLG-1050 Prefer the Higher-mass Solution

We report adaptive optics (AO) follow-up imaging of OGLE-2014-BLG-1050, which is the second binary microlensing event with space-based parallax measurements. The degeneracy in microlens parallax π_E led to two sets of solutions, either a ∼ (0.9, 0.35)M_⊙ binary at ∼3.5 kpc or a ∼(0.2, 0.07)M_⊙ binary at ∼1.1 kpc. We measure the flux blended with the microlensed source by conducting Magellan AO observations, and find that the blending is consistent with the predicted lens flux from the higher-mass solution. From the combination of the AO flux measurement together with previous lensing constraints, it is estimated that the lens system consists of a ${1.05}_{-0.07}^{+0.08}\,{M}_{\odot }$ primary and a ${0.38}_{-0.06}^{+0.07}{M}_{\odot }$ secondary at ${3.43}_{-0.21}^{+0.19}$ kpc. ^* This paper includes data gathered with the 6.5m Magellan Clay Telescope at Las Campanas Observatory, Chile.