Atmospheric Monitoring and Precise Spectroscopy of the HR 8799 Planets with SCExAO/CHARIS

Abstract

The atmospheres of gas giant planets are thought to be inhomogeneous due to weather and patchy clouds. We present two full nights of coronagraphic observations of the HR 8799 planets using the CHARIS integral field spectrograph behind the SCExAO adaptive optics system on the Subaru Telescope to search for spectrophomometric variability. We did not detect significant variability signals, but placed the lowest variability upper limits for HR 8799 c and d. Based on injection-recovery tests, we expected to have a 50% chance to detect signals down to 10% H-band photometric variability for HR 8799 c and down to 30% H-band variability for HR 8799 d. We also investigated spectral variability and expected a 50% chance to recovery 20% variability in the H/K flux ratio for HR 8799 c. We combined all the data from the two nights to obtain some of the most precise spectra obtained for HR 8799 c, d, and e. Using a grid of cloudy radiative-convective-thermochemical equilibrium models, we found all three planets prefer supersolar metallicity with effective temperatures of ~1100 K. However, our high signal-to-noise spectra show that HR 8799 d has a distinct spectrum from HR 8799 c, possibly preferring more vertically extended and uniform clouds and indicating that the planets are not identical.

21 pages, 12 figures, Accepted to AJ, time series photometry and stacked spectra available as text files

References in corpus (21)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9
• The Viewing Geometry of Brown Dwarfs Influences Their Observed Colours and Variability Properties
• Astrometry and Photometry with Coronagraphs
• Gemini Planet Imager Spectroscopy of the HR 8799 planets c and d
• Detection and Bulk Properties of the HR 8799 Planets with High Resolution Spectroscopy
• Accurate Astrometry and Photometry of Saturated and Coronagraphic Point Spread Functions
• Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: global and equatorial dynamics
• Deep Thermal Infrared Imaging of HR 8799 bcde: New Atmospheric Constraints and Limits on a Fifth Planet
• Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf
• HST Rotational Spectral Mapping of Two L-Type Brown Dwarfs: Variability In and Out of Water Bands Indicates High-Altitude Haze Layers
• Strong Near-Infrared Spectral Variability of the Young Cloudy L Dwarf Companion VHS J1256-1257 b
• 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
• A Chromaticity Analysis and PSF Subtraction Techniques for SCExAO/CHARIS data
• Vector speckle grid: instantaneous incoherent speckle grid for high-precision astrometry and photometry in high-contrast imaging

Cited by in corpus (8)

• Detecting exomoons from radial velocity measurements of self-luminous planets: application to observations of HR 7672 B and future prospects
• Roaring Storms in the Planetary-Mass Companion VHS 1256-1257 b: Hubble Space Telescope Multi-epoch Monitoring Reveals Vigorous Evolution in an Ultra-cool Atmosphere
• End-to-end numerical modeling of the Roman Space Telescope coronagraph
• JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO${}_2$ in the HR 8799 and 51 Eri Exoplanets' Atmospheres
• Measuring the variability of directly imaged exoplanets using vector Apodizing Phase Plates combined with ground-based differential spectrophotometry
• Global weather map reveals persistent top-of-atmosphere features on the nearest brown dwarfs
• Exploring the directly imaged HD 1160 system through spectroscopic characterization and high-cadence variability monitoring
• Post-processing CHARIS integral field spectrograph data with PyKLIP