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Roasting Marshmallows: Disentangling Composition & Climate in Hot Jupiter Atmospheres through High-Resolution Thermal Emission Cross-Correlation Spectroscopy

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Principle Investigator: Michael Line, Arizona State University, School of Earth and Space Exploration, Tempe AZ, USA

Program Summary:

Determining the nature of planetary atmospheres is a key objective of exoplanet science. A planet’s atmosphere contains a wealth of diagnostic information on basic planetary conditions like climate (temperature, dynamics) and composition--a tracer of planet formation. A planetary atmosphere can be probed via transit spectroscopy, with transmission (during primary transit) spectra, which senses the upper atmosphere along the limbs/terminator, dayside emission spectra (obtainable near secondary eclipse), which senses the integrated thermal properties of the planetary dayside, and phase resolved spectroscopy (obtainable at all other planetary phases) , which senses the longitudinal temperature and compositional distributions. This information has been primarily obtained at low resolution (R<~50) with space-based platforms like the Hubble and Spitzer Space Telescopes. However, a complimentary ground- based approach that leverages high spectral resolution and cross-correlation techniques has been steadily gaining traction, owing to the method’s high sensitivity to molecular detections, thermal structures, and global wind patterns, enabled by stable, broad wavelength coverage, high resolution spectrometers on large aperture telescopes. Our team has recently utilized IGRINS on Gemini South (GS-2020A- Q-218) to obtain a 13-sigma detection of molecular absorption lines (water and CO) via phase resolved hi-resolution cross-correlation emission spectroscopy of a ~1600K hot Jupiter during pre- and post- eclipse orbital phases. Such a strong detection enables precise constraints on the atmospheric C and O abundances and the vertical thermal structure at a level rivaling that expected from the James Webb Space Telescope. These preliminary results suggest that the broad wavelength coverage, high resolution , and stability of IGRINS combined with the large aperture on Gemini South makes this an ideal platform for a hot Jupiter emission spectroscopy survey. As such, we propose high spectral resolution phase- resolved cross- correlation emission spectroscopy survey of 15 hot Jupiters covering 1400 - 2600 K in order to diagnose the chemical, thermal, and dynamical mechanisms that drive key transitions in highly irradiated atmospheres. The proposed objects are estimated to have comparable planetary atmosphere detectability (relative thermal emission SNR’s ~ 0.5 - 1.5x, accounting for IQ85 conditions) as our initial detection. For all objects in the survey we will obtain the pre-eclipse phases (~2-6 hrs/planet) with additional visits (up to 6) for the more challenging (cooler) targets in our sample. Our resulting survey will require 131 hrs or spread out over 32 nights (some as half nights or less) over 6 semesters.


  • Jonathan Fortney: University of California-Sana Cruz
  • Nicolas Cowan: McGill University
  • Lisa Dang: McGill University
  • Megan Mansfield: University of Chicago
  • Jacob Bean: University of Chicago
  • Matteo Brogi: University of Warwick
  • Emily Rauscher: University of Michigan
  • Vivien Parmentier: University of Oxford
  • Peter Smith: Arizona State University
  • Joseph Zalesky: University of Arizona
  • Jennifer Patience: University of Arizona
  • Evgenya Shkolnik: Arizona State University
  • Callie Hood: University of California-Santa Cruz
  • Siddharth Gandhi: University of Warwick
  • Joost Wardenier (thesis): University of Oxford
  • Jean-Michel Desert: University of Amsterdam
  • Lorenzo Pino: INAF
  • Greg Mace: University of Texas-Austin
Roasting Marshmallows: Disentangling Composition & Climate in Hot Jupiter Atmospheres through High-Resolution Thermal Emission Cross-Correlation Spectroscopy | Gemini Observatory


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