The Department of Astronomy 2025-2026 Colloquium Series Presents:

Luke’s Title: Characterizing hot Jupiter atmospheres using Keck/KPIC high-resolution spectroscopy

Abstract: High-resolution cross-correlation spectroscopy (HRCCS) is a technique for characterizing the atmospheres of hot giant exoplanets by treating the system as a spectroscopic binary. Hot Jupiters near conjunction exhibit a rapid change in radial velocity relative to their host star, which can be used to isolate spectral features associated with the planet from stellar and telluric features. The HRCCS technique can be applied in transmission or emission, and is the only technique capable of characterizing atmospheres of close-in non-transiting planets. Since HRCCS directly detects planetary spectral features, this technique can be used to measure atmospheric composition, particularly the C/O ratio, and is also sensitive to atmospheric circulation effects via changes to the shapes of planetary spectral lines. Keck/KPIC has obtained HRCCS observations of approximately 20 hot Jupiters in the infrared K band, and complementary L band observations are ongoing. Initial results of this survey program include the characterization of benchmark hot Jupiters HD 189733 b and HD 209458 b, measuring the orbital inclination of the non-transiting hot Jupiter HD 143105 b, and the detection of six ultra-hot Jupiters with strong CO emission features. Ongoing work to combine these data with observations from other optical/infrared high-resolution spectrographs will enable measurement of refractory/volatile ratios for many of these planets. For objects observed at a wide range of orbital phases, HRCCS is a promising avenue for testing predictions from Global Circulation Models (GCMs) of hot Jupiter atmospheres.

Teresa’s Title: Multi-molecular analysis of turbulent motions during planet formation

Abstract: Turbulence is a key physical process expected to stir the planet-forming material in the early stages of planetary systems and act as an effective viscosity, aiding the evolution of protoplanetary disks. Even though it is a key phenomena, expected to have shaped our own Solar System, detection of turbulent motion has been scarce in the past years. This work presents an observationally motivated methodology that takes advantage of the high spatial and spectral resolution of ALMA observations to measure turbulence through molecular line broadening. By tracing distinct regions of the protoplanetary system through specific molecular tracers, we are able to resolve vertical variations in turbulent motions, obtaining the first insights into the physical instabilities that may be driving turbulence in these disks.