The Few-Body Problem in Microlensing: Enabling the Characterization of Roman's Exotic Microlensing Events
| Program ID | 19030 |
|---|---|
| Science Category | Exoplanets & Exoplanet Formation |
| Program Type | Analysis |
| Category | Medium |
| Principal Investigator | Bernard Gaudi |
| PI Institution | The Ohio State University |
| Co-Investigators |
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| Abstract | We propose a theoretical and computational investigation of the few-body problem in gravitational microlensing, focusing on lens systems with N≥3 point masses (but not N>>1). While most microlensing events have historically been modeled using single- or binary-lens formalisms, the improved survey cadence, photometric precision, and sample size of Roman will reveal a substantial population of events that cannot be robustly interpreted within this framework. Such events arise naturally in systems including multiplanet systems, circumbinary planets, planets orbiting one component of a stellar binary, and planets with satellites. To address this regime, we will develop a framework connecting caustic structure to practical light-curve inference. Our investigation focuses on a small set of physically motivated triple-lens architectures representative of realistic planetary systems. For these systems we will (1) classify caustic topologies and their transitions, (2) assess the validity and breakdown of commonly used approximations such as caustic and light-curve superposition, and (3) identify the physical origin of dominant degeneracies by relating caustic geometry to observable light-curve features. A key component is the use of machine-learning inference, specifically amortized neural posterior estimation, to explore the high-dimensional and highly degenerate parameter spaces of few-body lens systems. Machine learning will be used not as a black box, but as a discovery and validation tool linking posterior structure to caustic geometry. The outcome will be a computationally efficient framework for modeling and interpreting few-body microlensing events across modern surveys, enabling their reliable incorporation into demographic studies of planetary systems in the cold outer regions of planetary systems and supporting the goals of the Astro2020 Decadal Survey and NASA’s Exoplanet Exploration Program. |