Presentation #102.64 in the session Poster Session.
Hot and ultra-hot Jupiter atmospheres have three key observable components: composition, thermal structure, and atmospheric circulation in the form of circum-planetary winds that travel from the dayside to the nightside. The characteristics of these components are expected to change over the 2400 to 4800 K equilibrium temperature, 2.75 to 4.75 log surface gravity, and A to G dwarf host star spectral type of an eminently observable sub-set of the known population. We have started characterizing this survey population with the new fiber-fed high-resolution red-optical spectrograph MAROON-X with the dayside atmosphere of KELT-9b and KELT-20b through thermal emission observations at high significance. Our retrieval results for KELT-9b strongly preferred an inverted temperature profile and atomic/ion abundances largely consistent with the expectations for a solar composition gas in thermochemical equilibrium. For KELT-20b we see an inversion in the temperature profile, with abundances closer to 10x solar composition gas.