OGLE-2012-BLG-0563: Relative Proper Motion Constraint from Keck Follow-up finds the correct Lens
We present Keck/NIRC2 adaptive optics imaging results of planetary microlensing event OGLE-2012-BLG-0563. We find that the OGLE-2012-BLG-0563L planetary system consists of a 1.12 +/- 0.09 Jupiter-mass planet orbiting a 0.81 +/- 0.04 solar-mass host star at a distance of 5.49 +/- 0.56 kpc from the Sun. This event has a lens-source separation of 23.28 +/- 0.48 mas, which is the smallest lens-source separation measured to date with Keck AO data. We find that the incorrect solution - which identifies the Northeast (NE) star as the source star - is favored if one only considers the discovery paper, the Fukui et al. (2015) solution, or an unconstrained model. However, by performing an image-constrained light curve model fit using the relative proper motion direction constraint from the Keck follow-up data, we demonstrate that the correct solution identifies the NE star as the lens star. The discrepancy in the unconstrained models is driven by systematics in the FTS and MOA B & C data, alongside the impact of the relative proper motion direction constraints. This outcome offers two important lessons for future Roman data analysis: (1) thoroughly verify systematics across all passbands and identify the precise origin of chi-squared differences, and (2) utilize image-constrained light curve modeling incorporating relative proper motion direction constraints to identify the correct lens.