Collaborative Research: Revealing Exoplanet Atmospheres Using High-Resolution Spectroscopy

A team led by the University of Chicago and Arizona State University will carry out an observational program to help answer four science questions regarding the atmospheres of close-in giant planets orbiting distant stars: How do chemical abundances trace planet origins? How does atmosphere temperature depend on external radiation, gravity, and composition? How do the dynamic and magnetic fields of planets govern wind speeds? And what are atmosphere properties across chemical transitions? The team will train the science community in the use of new techniques for probing planet atmospheres with workshops. Workshops will focus upon early career researchers and will broaden participation by providing monetary support for junior scientists from underrepresented groups. Ground-based, high-resolution spectroscopy using the cross-correlation technique is a powerful, but complex method for probing exoplanet atmospheres. The project team have developed an atmospheric retrieval approach for cross-correlation spectroscopy which enables the extraction of detailed constraints on chemical compositions. The team will apply this technique to state-of-the-art high-resolution datasets to measure carbon-to-oxygen abundance ratios, atmospheric metallicity, carbon isotopic abundances, refractory species abundances, and how atmospheric temperature varies with pressure. The team will be carrying out a survey using three of the most sensitive high-resolution spectrographs: IGRINS on Gemini South, MAROON-X on Gemini North, and ESPRESSO on the VLT. These instruments span the optical to the near-infrared, yielding access to spectroscopic lines from major refractory (Fe, Ti, V) and volatile (C, N, O) elements and their isotopologues (C, Ti) in a variety of atomic and molecular species. The surveys will utilize both transmission and phase-resolved thermal emission measurements, targeting more than 30 planets with a broad range of physical parameters. Workshop attendees will be walked through how to prepare observations and the full end-to-end reduction and analysis of high-resolution data. The workshop lectures will be recorded and posted online and a suite of data analysis and atmospheric retrieval software will be made publicly available. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.