Resolving chemical gradients in exoplanet atmospheres with high-resolution spectroscopy

Ultra-hot Jupiters (UHJs) are gas giant planets like Jupiter that orbit so close to their host star that they are tidally locked, causing a permanent hot dayside and a cooler cloudy nightside. The atmospheres of UHJs can be uniquely probed using high-resolution transit transmission spectroscopy by resolving time dependent velocity shifts as the planet rotates and varying areas of the evening and morning terminator are probed. These velocity shifts were seen for the first time with iron absorption in WASP-76b. In this talk, I will present our comprehensive search for other species in WASP-76b’s transmission spectrum and our subsequent detections of Li I, Na I, Mg I, Ca II, V I, Cr I, Mn I, Fe I, Ni I, and Sr II, and tentative detections of H I, K I, and Co I. We then compare the observed time-dependent velocity shifts for each of the detected species, and find a correlation between the expected condensation or ionization temperatures and the strength of the shift, which indicates that some species rain-out or recombine on the nightside of the planet while others do not. Finally, I will discuss how we can use this technique to probe cloud formation and wind flows across the surface of the planet.