Leveraging Photometry for Deconfusion of Directly Imaged Multi-Planet Systems

Abstract: Planned and future missions, including the Habitable Worlds Observatory (HWO), will aim to directly image Earth-like exoplanets around Sun-like stars in reflected light. Determining whether an exoplanet is in the habitable zone of its star may be difficult in multi-planet systems when the observer does not know in advance which point source detection corresponds to which planet. This "confusion" problem will be a concern for future missions due to the high occurrence rate of multi-planet systems, and will be exacerbated by lack of prior knowledge about planets' orbital parameters or characteristics, particularly for systems at high inclination with respect to the observer. This work addresses the confusion problem by developing a photometry model and new orbit ranking function to augment the "deconfuser" tool and account for phase variation exhibited by a planet throughout its orbit. We demonstrate the new ranking scheme on a subset of thirty highly confused simulated multi-planet systems among three inclination groupings (low, medium, and high). Results indicate that photometry improves differentiation of previously confused orbits in 7/10 of the low inclination cases, 6/10 of the medium inclination cases, and 6/10 of the high inclination cases. This improvement in handling highly confused systems emphasizes that photometry shows promise for supporting orbit discrimination and deconfusion of directly imaged multi-planet systems, and should be considered when fitting orbits to detections.