Gemini Planet Imager Spectroscopy of the HR 8799 planets c and d

Abstract

During the first-light run of the Gemini Planet Imager (GPI) we obtained K-band spectra of exoplanets HR 8799 c and d. Analysis of the spectra indicates that planet d may be warmer than planet c. Comparisons to recent patchy cloud models and previously obtained observations over multiple wavelengths confirm that thick clouds combined with horizontal variation in the cloud cover generally reproduce the planets' spectral energy distributions. When combined with the 3 to 4 um photometric data points, the observations provide strong constraints on the atmospheric methane content for both planets. The data also provide further evidence that future modeling efforts must include cloud opacity, possibly including cloud holes, disequilibrium chemistry, and super-solar metallicity.

Accepted for publication in ApJ

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• Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: effects of rotation
• Detection and Bulk Properties of the HR 8799 Planets with High Resolution Spectroscopy
• A Direct Imaging Survey of Spitzer detected debris disks: Occurrence of giant planets in dusty systems
• Deep exploration of the planets HR 8799 b, c, and d with moderate resolution spectroscopy
• The SPHERE infrared survey for exoplanets (SHINE)- I Sample definition and target characterization
• The LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system
• On the Composition of Young, Directly Imaged Giant Planets
• Assessing the C/O Ratio Formation Diagnostic: A Potential Trend with Companion Mass
• A search for a 5th planet around HR 8799 using the star-hopping RDI technique at VLT/SPHERE
• Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY
• On the Chemical Abundance of HR 8799 and the Planet c
• Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets
• A High-Contrast Search for Variability in HR 8799bc with VLT-SPHERE
• Cloud Atlas: High-Contrast Time-Resolved Observations of Planetary-Mass Companions
• Imaging detection of the inner dust belt and the four exoplanets in the HR8799 system with JWST's MIRI coronagraph
• Early Results from VLT-SPHERE: Long-Slit Spectroscopy of 2MASS 0122-2439B, a Young Companion Near the Deuterium Burning Limit
• Atmospheric Monitoring and Precise Spectroscopy of the HR 8799 Planets with SCExAO/CHARIS
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• The Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT): An Open-Source Tool for Efficient Fitting of Astrometric and Radial Velocity Data
• Combining angular differential imaging and accurate polarimetry with SPHERE/IRDIS to characterize young giant exoplanets
• Impacts of high-contrast image processing on atmospheric retrievals
• The post-main-sequence fate of the HR 8799 planetary system
• The infrared colors of 51 Eridani b: micrometereoid dust or chemical disequilibrium?
• High Spatial Resolution Thermal-Infrared Spectroscopy with ALES: Resolved Spectra of the Benchmark Brown Dwarf Binary HD 130948BC
• Illusion and Reality in the Atmospheres of Exoplanets