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Predicted Yields of the TESS-Keck Survey’s Atmospheric Sample with JWST Observations

Presentation #102.220 in the session Poster Session.

Published onJun 20, 2022
Predicted Yields of the TESS-Keck Survey’s Atmospheric Sample with JWST Observations

In this poster, we will present anticipated atmospheric yields from the TESS-Keck Survey (TKS), which has been performing precise radial velocity (RV) followup on TESS planet candidates for the past two years. The atmospheres working group within TKS has been focused on identifying the best targets for follow up with the James Webb Space Telescope (JWST). With our planet sample now mostly in hand, we present detectability metrics for atmospheric molecular abundances given various assumptions about cloudiness and metallicity. Our sample contains 24 planets, of which two still have ambiguous periods. We establish a target minimum signal-to-noise ratio (SNR) value of 5 for the largest spectral feature in each object’s atmospheric transmission spectrum. With that requirement, up to 6 of our planets could be included in a small program (<25 hours), 13 in a medium program (25-75 hours), and up to 18 in a hypothetical large program (>75 hours) comparable to the largest exoplanet program accepted in Cycle 1 GO (142 hours). With recent optimism that JWST will be fuel-limited, extending the mission lifespan years beyond what was previously believed, it is reasonable to imagine that over multiple cycles, we could achieve our desired SNR across our entire 24 planet sample with a total of 193 hours of JWST observations. Several of our targets, such as HD 191939 and HD 63935, are multi-planet systems with the potential to produce higher SNR atmospheric transit signals than any other planets with comparable properties. Our target selection function seeks to uniformly sample planet radius, insolation, and host star spectral type, weighted by time to a 5-sigma mass with Keck HIRES which favors G and K type host stars. A library of high-SNR spectra for this entire sample would represent a great boon in our understanding of planetary formation and atmospheric processes, particularly for the sub-Neptune population. In particular, our sample covers a domain that ranges from the upper edge of the “radius cliff” past 3 REarth and down to the radius gap at 1.7 REarth. Atmospheric measurements of this sample of planets could elucidate the processes that have been hypothesized to sculpt these observed features in the mass-radius distribution, as well as the role that irradiation plays in the evolution of sub-Neptune planetary envelopes. The lower end of our radius sample could also help understand the divide between sub-Neptune and super-Earth exoplanets.

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