Prospects for Characterizing the Haziest Sub-Neptune Exoplanets with High Resolution Spectroscopy

Abstract

Observations to characterize planets larger than Earth but smaller than Neptune have led to largely inconclusive interpretations at low spectral resolution due to hazes or clouds that obscure molecular features in their spectra. However, here we show that high-resolution spectroscopy (R $\sim$ 25,000 to 100,000) enables one to probe the regions in these atmospheres above the clouds where the cores of the strongest spectral lines are formed. We present models of transmission spectra for a suite of GJ1214b-like planets with thick photochemical hazes covering 1 - 5 $\mu$m at a range of resolutions relevant to current and future ground-based spectrographs. Furthermore, we compare the utility of the cross-correlation function that is typically used with a more formal likelihood-based approach, finding that only the likelihood based method is sensitive to the presence of haze opacity. We calculate the signal-to-noise of these spectra, including telluric contamination, required to robustly detect a host of molecules such as CO, CO${}_2$, H${}_2$O, and CH${}_4$, and photochemical products like HCN, as a function of wavelength range and spectral resolution. Spectra in M band require the lowest S/N${}_{res}$ to detect multiple molecules simultaneously. CH${}_4$ is only observable for the coolest models ($T_{\mathrm{eff}}=$ 412 K) and only in the L band. We quantitatively assess how these requirements compare to what is achievable with current and future instruments, demonstrating that characterization of small cool worlds with ground-based high resolution spectroscopy is well within reach.

arXiv commentSubmitted to AAS Journals, revised to reflect referee comments. Posting of this manuscript on the arXiv was coordinated with S. Ghandi et al

References in corpus (88)

• The Transiting Exoplanet Survey Satellite
• Bayes in the sky: Bayesian inference and model selection in cosmology
• The false positive rate of Kepler and the occurrence of planets
• Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
• Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data
• The effects of snowlines on C/O in planetary atmospheres
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b
• Prevalence of Earth-size planets orbiting Sun-like stars
• A super-Earth transiting a nearby low-mass star
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• A high accuracy computed water line list
• A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
• The Transiting Exoplanet Survey Satellite: Simulations of planet detections and astrophysical false positives
• Infrared Transmission Spectroscopy of the Exoplanets HD209458b and XO-1b Using the Wide Field Camera-3 on the Hubble Space Telescope
• ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K
• Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres
• A ground-based transmission spectrum of the super-Earth exoplanet GJ1214b
• Characterizing transiting exoplanet atmospheres with JWST
• Detection of water absorption in the day side atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 microns
• Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres over a Range of Metallicities and Temperatures
• Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
• A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b
• A Framework for Quantifying the Degeneracies of Exoplanet Interior Compositions
• A Framework for Characterizing the Atmospheres of Low-Mass Low-Density Transiting Planets
• An atmospheric radiation model for Cerro Paranal. I. The optical spectral range
• Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b
• A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)
• Imaging Spectroscopy for Extrasolar Planet Detection
• Water Vapour Absorption in the Clear Atmosphere of an exo-Neptune
• Retrieving Temperatures and Abundances of Exoplanet Atmospheres with High-Resolution Cross-Correlation Spectroscopy
• Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)
• Thermal Emission and Albedo Spectra of Super Earths with Flat Transmission Spectra
• Rotation and winds of exoplanet HD 189733 b measured with high-dispersion transmission spectroscopy
• 55 Cancri (Copernicus): A Multi-Planet System with a Hot Super-Earth and a Jupiter Analogue
• Chemical enrichment of giant planets and discs due to pebble drift
• Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST
• Planetary Candidates Observed by Kepler IV: Planet Sample From Q1-Q8 (22 Months)
• Quantitatively Assessing the Role of Clouds in the Transmission Spectrum of GJ 1214b
• Hubble Space Telescope Near-IR Transmission Spectroscopy of the Super-Earth HD 97658b
• Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy
• The Optical and Near-Infrared Transmission Spectrum of the Super-Earth GJ1214b: Further Evidence for a Metal-Rich Atmosphere
• An advanced scattered moonlight model for Cerro Paranal
• Thermal evolution and structure models of the transiting super-Earth GJ 1214b
• Planetary Candidates Observed by Kepler V: Planet Sample from Q1-Q12 (36 Months)
• Carbon monoxide and water vapor in the atmosphere of the non-transiting exoplanet HD 179949 b
• The Atmospheric Chemistry of GJ 1214b: Photochemistry and Clouds
• Weighing The Non-Transiting Hot Jupiter Tau BOO b
• Understanding Trends Associated with Clouds in Irradiated Exoplanets
• Quantifying and Predicting the Presence of Clouds in Exoplanet Atmospheres
• Discovery of water at high spectral resolution in the atmosphere of 51 Peg b
• Trends in Atmospheric Properties of Neptune-Size Exoplanets
• SPIRou: the near-infrared spectropolarimeter/high-precision velocimeter for the Canada-France-Hawaii telescope
• Exoplanet atmospheres with GIANO. I. Water in the transmission spectrum of HD 189733b
• Vibrational transition moments of CH${}_4$ from first principles
• Metal enrichment leads to low atmospheric C/O ratios in transiting giant exoplanets
• Water, High-Altitude Condensates, and Possible Methane Depletion in the Atmosphere of the Warm Super-Neptune WASP-107b
• High Resolution, Differential, Near-infrared Transmission Spectroscopy of GJ 1214b
• On the robustness of analysis techniques for molecular detections using high resolution exoplanet spectroscopy
• The slow spin of the young sub-stellar companion GQ Lupi b and its orbital configuration
• Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets
• Microphysics of KCl and ZnS Clouds on GJ 1214b
• Exoplanet atmospheres with GIANO II. Detection of molecular absorption in the dayside spectrum of HD 102195b
• Evidence for multiple molecular species in the hot Jupiter HD 209458b
• A Characteristic Transmission Spectrum dominated by H${}_2$O applies to the majority of HST/WFC3 exoplanet observations
• Search for water in a super-Earth atmosphere: High-resolution optical spectroscopy of 55 Cancri e
• Multiple water band detections in the CARMENES near-infrared transmission spectrum of HD 189733 b
• Warm Ice Giant GJ 3470b. I. A Flat Transmission Spectrum Indicates a Hazy, Low-methane, and/or Metal-rich Atmosphere
• The Impact of Stellar Rotation on the Detectability of Habitable Planets Around M Dwarfs
• Simulated JWST/NIRISS Transit Spectroscopy of Anticipated TESS Planets Compared to Select Discoveries from Space-Based and Ground-Based Surveys
• Exploring Exoplanet Cloud Assumptions in \textit{JWST} Transmission Spectra
• Identifying new opportunities for exoplanet characterisation at high spectral resolution
• Ground- and Space-based Detection of the Thermal Emission Spectrum of the Transiting Hot Jupiter KELT-2Ab
• A Theory of Exoplanet Transits with Light Scattering
• Bulk composition of the transiting hot Neptune around GJ 436
• A H13CN/HN13C linelist, model atmospheres and synthetic spectra for carbon stars
• AIC, BIC, Bayesian evidence against the interacting dark energy model
• HST PanCET program: A Cloudy Atmosphere for the promising JWST target WASP-101b
• High Resolution Transmission Spectroscopy as a Diagnostic for Jovian Exoplanet Atmospheres: Constraints from Theoretical Models
• Exoplanet Atmospheres at High Spectral Resolution
• Exoplanet Atmosphere Forecast: Observers Should Expect Spectroscopic Transmission Features to be Muted to 33%
• Diagnosing aerosols in extrasolar giant planets with cross-correlation function of water bands
• CO Detected in CI Tau b: Hot Start Implied by Planet Mass and M${}_K$
• Planet and star synergy at high spectral resolution. A rationale for the characterisation of exoplanet atmospheres. I. The Infrared
• High-Resolution Transit Spectroscopy of Warm Saturns
• Constraining Exoplanet Metallicities and Aerosols with ARIEL: An Independent Study by the Contribution to ARIEL Spectroscopy of Exoplanets (CASE) Team
• High-resolution Infrared Spectrograph for Exoplanet Characterization with the Keck and Thirty Meter Telescopes

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• On The Synergy Between Ariel And Ground-Based High-Resolution Spectroscopy
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