Physical Lens Constraints for Legacy MOA Microlensing Events with the Roman GPS
| Program ID | 19026 |
|---|---|
| Science Category | Exoplanets & Exoplanet Formation |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Shota Miyazaki |
| PI Institution | Institute of Space and Astronautical Science |
| Co-Investigators |
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| Abstract | Gravitational microlensing has revealed a distinctive population of cold planets, low-mass hosts, and compact objects toward the inner Galaxy. For most legacy events, however, the lens remains only weakly characterized because the light curve constrains the system mainly in Einstein units rather than in directly physical quantities. This program will use Roman Galactic Plane Survey (GPS) imaging to place late-time, high-angular-resolution constraints on source--lens configurations and convert the legacy MOA archive into a physically interpretable lens sample. We focus on the MOA-defined event sample because, in crowded Galactic fields, the true microlensed source generally cannot be identified on the Roman frame by catalog matching alone. Instead, it must be reconstructed from the original survey images. The MOA archive is well-suited to this because it provides homogeneous time-series and difference-imaging data across a large historical sample. We will combine MOA-based source reconstruction with Roman GPS cutouts to identify counterparts and derive lens-flux and source--lens-separation constraints, which will then be translated into constraints on lens mass, distance, and planetary-system scale. The long baseline between the MOA event epoch and the Roman imaging epoch makes these constraints substantially more informative for many systems. Because the GPS footprint also overlaps nearly the full spatial distribution of past MOA events and includes a larger disk-lens fraction than the Roman bulge time-domain survey, the resulting sample will support population-level comparisons across Galactic environments. The main Cycle 1 product will be a homogeneous Roman-based characterization of legacy MOA events and the first selection-aware constraints on the physical lens population recoverable from this archive. |