The Observations Needed to Constrain Exoplanet Orbits and Masses for Ariel/CASE & JWST

Exoplanetary astrophysics has entered a new era of exoplanet characterization thanks to continually evolving ground-based instruments and anticipated observations with JWST and ESA’s Ariel mission. JWST will observe hundreds of planets in the infrared during its lifetime, while Ariel is expected to conduct visible to near-infrared spectroscopy of 1000+ exoplanet atmospheres — with the community drawing targets from the both the list of confirmed exoplanets and the list of the best TESS (and eventually PLATO) candidates.This new era of precise atmospheric characterization across hundreds if not thousands of targets requires ephemerides good enough to predict the times of transits and eclipses so as to not waste precious telescope time, or worse, miss the transits or eclipses. These efforts will also rely on precise (>5σ) measurements of the planets’ masses to determine their surface gravities and scale heights, which in turn limit the degeneracies present when interpreting results from Ariel and/or JWST atmospheric retrievals.

Here we present an initial study on the amount of precursor observational work required to ensure not only the efficient use of large ground- and space-based observatories but also the interpretation of their spectroscopic data. Results from this study will help support future transit observations with any large ground- or space-based platform, such as HST, JWST, or the future 6-m direct imaging mission recommended by the Astro2020 Decadal Survey.