CROCODILE \\ Incorporating medium-resolution spectroscopy of close-in directly imaged exoplanets into atmospheric retrievals via cross-correlation

Abstract

The investigation of the atmospheres of closely separated, directly imaged gas giant exoplanets is challenging due to the presence of stellar speckles that pollute their spectrum. To remedy this, the analysis of medium- to high-resolution spectroscopic data via cross-correlation with spectral templates (cross-correlation spectroscopy) is emerging as a leading technique. We aim to define a robust Bayesian framework combining, for the first time, three widespread direct-imaging techniques, namely photometry, low-resolution spectroscopy, and medium-resolution cross-correlation spectroscopy in order to derive the atmospheric properties of close-in directly imaged exoplanets. Our framework CROCODILE (cross-correlation retrievals of directly imaged self-luminous exoplanets) naturally combines the three techniques by adopting adequate likelihood functions. To validate our routine, we simulated observations of gas giants similar to the well-studied $\beta$~Pictoris~b planet and we explored the parameter space of their atmospheres to search for potential biases. We obtain more accurate measurements of atmospheric properties when combining photometry, low- and medium-resolution spectroscopy into atmospheric retrievals than when using the techniques separately as is usually done in the literature. We find that medium-resolution ($R\approx 4000$) K-band cross-correlation spectroscopy alone is not suitable to constrain the atmospheric properties of our synthetic datasets; however, this problem disappears when simultaneously fitting photometry and low-resolution ($R\approx 60$) spectroscopy between the Y and M bands. Our framework allows the atmospheric characterisation of directly imaged exoplanets using the high-quality spectral data that will be provided by the new generation of instruments such as VLT/ERIS, JWST/MIRI, and ELT/METIS.

References in corpus (32)

• The Gemini Planet Imager: First Light
• petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
• On the radiative equilibrium of irradiated planetary atmospheres
• Two accreting protoplanets around the young star PDS 70
• The imprint of exoplanet formation history on observable present-day spectra of hot Jupiters
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• Tau-REx I: A next generation retrieval code for exoplanetary atmospheres
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
• Observing transiting planets with JWST -- Prime targets and their synthetic spectral observations
• The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b
• The ExoMolOP Database: Cross-sections and k-tables for Molecules of Interest in High-Temperature Exoplanet Atmospheres
• Peering into the formation history of beta Pictoris b with VLTI/GRAVITY long baseline interferometry
• GENESIS: New Self-Consistent Models of Exoplanetary Spectra
• Excess C/O and C/H in outer protoplanetary disk gas
• Retrieval of Exoplanet Emission Spectra with HyDRA
• Detection and Bulk Properties of the HR 8799 Planets with High Resolution Spectroscopy
• Radial Velocity Measurements of HR 8799 b and c with Medium Resolution Spectroscopy
• A Clear View of a Cloudy Brown Dwarf Companion from High-Resolution Spectroscopy
• The SPHERE infrared survey for exoplanets (SHINE) -- II. Observations, Data reduction and analysis Detection performances and early-results
• The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks
• Deep exploration of the planets HR 8799 b, c, and d with moderate resolution spectroscopy
• A medium-resolution spectrum of the exoplanet HIP 65426 b
• Large Interferometer For Exoplanets (LIFE): III. Spectral resolution, wavelength range and sensitivity requirements based on atmospheric retrieval analyses of an exo-Earth
• Assessing the C/O Ratio Formation Diagnostic: A Potential Trend with Companion Mass
• Peering into the Young Planetary System AB Pic. Atmosphere, Orbit, Obliquity & Second Planetary Candidate
• On the Chemical Abundance of HR 8799 and the Planet c
• Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-Resolution Data
• Molecular mapping of the PDS70 system: No molecular absorption signatures from the forming planet PDS70 b
• Direct emission spectroscopy of exoplanets with the medium resolution imaging spectrometer on board JWST MIRI: I. Molecular mapping and sensitivity to instrumental effects
• If you like C/O variations, you should have put a ring on it
• Making SPIFFI SPIFFIER: Upgrade of the SPIFFI instrument for use in ERIS and performance analysis from re-commissioning
• High signal-to-noise spectral characterization of the planetary-mass object HD 106906 b

Cited by in corpus (4)

• Large Interferometer For Exoplanets (LIFE): XIII. The Value of Combining Thermal Emission and Reflected Light for the Characterization of Earth Twins
• Multi-modal atmospheric characterization of $\beta$ Pictoris b: Adding high-resolution continuum spectra from GRAVITY
• Machine Learning for Exoplanet Detection in High-Contrast Spectroscopy: Revealing Exoplanets by Leveraging Hidden Molecular Signatures in Cross-Correlated Spectra with Convolutional Neural Networks
• High-contrast spectroscopy with the new VLT/ERIS instrument: Molecular maps and radial velocity of the gas giant AF Lep b