The Role of Exoplanet Photometry in Orbit-Fitting of Directly Imaged Multi-Planet Systems

Direct imaging observations of exoplanets will help identify Earth-like planets around Sun-like stars. Planned and future missions, such as the Large space-based Infrared/Optical/Ultraviolet (IR/O/UV) Telescope prioritized in Astro2020, are planned to have instrumentation capable of exoplanet direct imaging, such as a coronagraph and wavefront sensing and control system. Determining whether a planet is in the habitable zone of its star may be difficult in multi-planet systems, which are now known to occur frequently. Previous work (Keithly et al. 2021) has shown that planets in multi-planet systems can be “confused” in direct images of a system taken over multiple epochs due to lack of prior knowledge about the planets’ orbital parameters or planetary characteristics. Being able to differentiate planets in multi-planet systems is necessary in order to determine orbital parameters, perform observation scheduling, characterize atmospheres, and determine habitability. In this work, we address the confusion problem using photometric observations, such as planetary orbital phase, in a “deconfusion” algorithm to help differentiate between multiple planets in an image.

The deconfusion algorithm our team has developed is designed to accept unlabeled detections of planets, accompanied by astrometric information, and generate a list of orbit parameter matches constrained by an eccentricity threshold. The matches are then ranked based on their consistency with the presented data and the number of matched observations. However, this method of ranking alone may not be enough to solve the confusion and observation scheduling problem. We introduce the inclusion of orbital phase considerations in the deconfusion algorithm to help rank and further differentiate the matched orbit combinations. With a large number of simulated planetary systems, we are investigating the utility of orbital phase (color, intensity) information for each planet to reduce the rate of confusion in a multi-planet system. We present preliminary orbit matching rates for planets that include simulated photometric information. Our results will be used to determine the ability of photometric information to mitigate confusion and improve observation scheduling techniques for future direct imaging missions.