OPTIMIZING JWST EXOPLANETARY ATMOSPHERIC CHARACTERIZATION THROUGH PRIORITIZATION AND VALIDATION OF TESS-DISCOVERED EXOPLANETS AND PANCHROMATIC STUDIES
Louie, Dana Renee
Deming, L. Drake
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The approaching launch of the James Webb Space Telescope (JWST), coupled with the recent all-sky search of the Transiting Exoplanet Survey Satellite (TESS), heralds a new era in exoplanetary atmospheric characterization, with TESS projected to detect over one thousand transiting exoplanets smaller than Neptune, and JWST offering unprecedented spectroscopic capabilities. My work focuses on optimizing future observations in three ways. First, JWST time and resources will not allow observations of all TESS discoveries, so we must prioritize exoplanets for atmospheric characterization. I simulated JWST transmission spectroscopy observations of the anticipated TESS planet yield and compared the results to simulated transmission spectroscopy observations of already known exoplanets. My most significant finding is that several hundred TESS 1.5 to 2.5 Earth radii sub-Neptunes can be observed at higher signal-to-noise than currently known similarly-sized exoplanets. My work was used as the basis in developing the Kempton et al. (2018) Transmission Spectroscopy Metric (TSM), which is widely used by the exoplanet atmosphere community in prioritizing which exoplanets to observe with JWST. Second, predictions show that TESS will detect thousands of astrophysical false positives that mimic exoplanet discoveries by also producing periodic decreases in starlight. A common scenario occurs when light from the target star blends with that of nearby eclipsing binary stars. Thus, TESS discoveries must be validated as true exoplanets using additional instruments or techniques. I designed software codes to predict how well two multi-band photometry instruments can discriminate between blended eclipsing binary false positives and true exoplanets. I found that the instruments can validate hundreds of candidate exoplanets smaller in size than Neptune. Finally, previous atmospheric characterization studies have shown that observations using only infrared instruments---such as those used by JWST---may produce ambiguous atmospheric compositions. An exoplanet atmosphere may be more clearly understood by analyzing observations across multiple wavelength regimes. I analyzed Hubble Space Telescope (HST) transmission spectroscopy data for the hot Jupiter KELT-7b across wavelengths from the near ultraviolet to near infrared. This panchromatic analysis helps us better understand observations we can use to complement the near and mid-infrared observations of JWST, which is particularly important while HST is still operational.