Combined Exoplanet Mass and Atmospheric Characterization for Accelerated Exoplanetology

Abstract

Today's most detailed characterization of exoplanet atmospheres is accessible via transit spectroscopy (TS). Detecting transiting exoplanets only yields their size, and it is thus standard to measure a planet's mass before moving towards their atmospheric characterization, or even the publication of their discovery. This framework, however, can act as a bottleneck for high-throughput exoplanetology. Here, we review existing applications of an alternative approach deriving exoplanet masses in small JWST atmospheric exploration programs and quantify the potential of its systematic application. We find that for $\sim$20\% of transiting exoplanets with existing mass constraints, a small JWST exploration program could yield the planetary mass with a similar -- or better -- precision. Such results suggest that proceeding directly with atmospheric exploration programs for favorable exoplanets (i.e., with a transmission spectroscopy metric, TSM, $\geq$100) could substantially reduce the time from detection to exoplanet atmospheric study and further support JWST's scientific output over its lifetime while saving up to 20\% of resources on radial-velocity (RV) facilities. Furthermore, it can substantially increase the sample of characterized planets of three distinct subpopulations (Neptune-sized, young, and hot-star exoplanets), each providing specific insights into formation and evolution processes. As the field of exoplanets increasingly turns to directly imaged planets, mastering the determination of planetary masses from atmospheric spectra will become essential.