A Framework for Prioritizing the <i>TESS</i> Planetary Candidates Most Amenable to Atmospheric Characterization

Abstract

A key legacy of the recently launched TESS mission will be to provide the\nastronomical community with many of the best transiting exoplanet targets for\natmospheric characterization. However, time is of the essence to take full\nadvantage of this opportunity. JWST, although delayed, will still complete its\nnominal five year mission on a timeline that motivates rapid identification,\nconfirmation, and mass measurement of the top atmospheric characterization\ntargets from TESS. Beyond JWST, future dedicated missions for atmospheric\nstudies such as ARIEL require the discovery and confirmation of several hundred\nadditional sub-Jovian size planets (R_p &lt; 10 R_Earth) orbiting bright stars,\nbeyond those known today, to ensure a successful statistical census of\nexoplanet atmospheres. Ground-based ELTs will also contribute to surveying the\natmospheres of the transiting planets discovered by TESS. Here we present a set\nof two straightforward analytic metrics, quantifying the expected\nsignal-to-noise in transmission and thermal emission spectroscopy for a given\nplanet, that will allow the top atmospheric characterization targets to be\nreadily identified among the TESS planet candidates. Targets that meet our\nproposed threshold values for these metrics would be encouraged for rapid\nfollow-up and confirmation via radial velocity mass measurements. Based on the\ncatalog of simulated TESS detections by Sullivan et al. (2015), we determine\nappropriate cutoff values of the metrics, such that the TESS mission will\nultimately yield a sample of $\\sim300$ high-quality atmospheric\ncharacterization targets across a range of planet size bins, extending down to\nEarth-size, potentially habitable worlds.\n