Atmospheric Characterization of HD209458b and HD189733b with High Resolution Cross Correlation Spectroscopy

High Resolution Cross Correlation Spectroscopy (HRCCS) has become a powerful tool to constrain both the physical characteristics and abundances of atomic/molecular constituents in exoplanetary atmospheres. Brogi & Line (2019) recently introduced a novel Bayesian atmospheric retrieval methodology that can combine observations from both longer wavelength (2-4 micron), ground-based, HRCCS and shorter wavelength (1-2 micron) space-based observatories such as the Hubble Space Telescope (HST). Here we present results from the first application of this technique to both new and previously published observations of HD209458b and HD189733b from VLT/CRIRES, HST, and Spitzer. The more complete wavelength coverage provides a more comprehensive assessment of the atmosphere by way of stronger constraints on the thermal profiles, atmospheric metallicity, and carbon/oxygen inventory for these two benchmark planets. We also investigate the impact of possible model-induced biases including assumptions regarding molecular cross-sections, cloud model prescriptions, and thermal profile parameterizations. Finally, we present what constraints may be possible in the future by performing retrievals of synthetic observations from the next generation of high-resolution spectrographs like CRIRES+. This work has laid a foundational dataset that combines both space and ground-based observations to comprehensively characterize exoplanetary atmospheres and will be a useful benchmark in comparison to future efforts for both transiting and non-transiting atmospheric characterization.