Analytic Stability Maps of Unknown Exoplanet Companions for Imaging Prioritization

Abstract

Abstract Identifying which systems are more likely to host an imageable planet can play an important role in the construction of an optimized target list for future direct imaging missions, such as the planned Coronagraph Instrument (CGI) technology demonstration for the Nancy Grace Roman Space Telescope. For single-planet systems, the presence of an already detected exoplanet can severely restrict the target’s stable region and should therefore be considered when searching for unknown companions. To do so, we first analyze the performance and robustness of several two-planet stability criteria by comparing them with long-term numerical simulations. We then derive the necessary formulation for the computation of (a, R) analytic stability maps, which can be used in conjunction with depth-of-search grids in order to define the stable-imageable region of a system. The dynamically stable completeness (i.e., the expected number of imageable and stable planets) can then be calculated via convolution with the selected occurrence grid, obtaining a metric that can be directly compared for imaging prioritization. Applying this procedure to all the currently known single-planet systems within a distance of 50 pc, we construct a ranked target list based on the CGI’s predicted performance and SAG13 occurrence rates. Finally, we evaluate the importance of considering the radial velocity data from past Doppler surveys in order to rule out entire regions of our parameter space where, if a planet existed, it would have certainly been detected by previous RV observations.