Arid or Cloudy: Characterizing the Atmosphere of the super-Earth 55 Cancri e using High-Resolution Spectroscopy

Abstract

The nearby super-Earth 55 Cnc e orbits a bright (V = 5.95 mag) star with a period of ~ 18 hours and a mass of ~ 8 Earth masses. Its atmosphere may be water-rich and have a large scale-height, though attempts to characterize it have yielded ambiguous results. Here we present a sensitive search for water and TiO in its atmosphere at high spectral resolution using the Gemini North telescope and the GRACES spectrograph. We combine observations with previous observations from Subaru and CFHT, improving the constraints on the presence of water vapor. We adopt parametric models with an updated planet radius based on recent measurements, and use a cross-correlation technique to maximize sensitivity. Our results are consistent with atmospheres that are cloudy or contain minimal amounts of water and TiO. Using these parametric models, we rule out a water-rich atmosphere (VMR >= 0.1%) with a mean molecular weight of <= 15 g/mol at a 3 sigma confidence level, improving on the previous limit by a significant margin. For TiO, we rule out a mean molecular weight of <= 5 g/mol with a 3 sigma confidence level for a VMR greater than 10^-8; for a VMR of greater than 10^-7, the limit rises to a mean molecular weight of <= 10 g/mol. We can rule out low mean-molecular-weight chemical equilibrium models both including and excluding TiO/VO at very high confidence levels (> 10 sigma). Overall, our results are consistent with an atmosphere with a high mean molecular weight and/or clouds, or no atmosphere.

15 pages, 12 figures, 1 table

References in corpus (18)

• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST
• A Sub-Neptune Exoplanet with a Low-Metallicity Methane-Depleted Atmosphere and Mie-Scattering Clouds
• Radius and Structure models for the First Super-Earth Planet
• ExoMol line lists XVIII. The high temperature spectrum of VO
• High-Resolution Spectroscopic Detection of TiO and Stratosphere in the Day-side of WASP-33b
• A search for TiO in the optical high-resolution transmission spectrum of HD 209458b: Hindrance due to inaccuracies in the line database
• Probing the Blow-Off Criteria of Hydrogen-Rich "Super-Earths"
• A new class of Super-Earths formed from high-temperature condensates: HD219134 b, 55 Cnc e, WASP-47 e
• Linking the Climate and Thermal Phase Curve of 55 Cancri e
• A Case for an Atmosphere on Super-Earth 55 Cancri e
• Cloud formation in metal-rich atmospheres of hot super-Earths like 55 Cnc e and CoRot7b
• Limits on the 2.2 microns contrast ratio of the close orbiting planet HD 189733b
• GRACES: Gemini remote access to CFHT ESPaDOnS Spectrograph through the longest astronomical fiber ever made (Experimental phase completed.)
• Near infrared spectroscopic search for the close orbiting planet HD 75289b
• HD 75289Ab revisited - Searching for starlight reflected from a hot Jupiter
• HD 179949b: A Close Orbiting Extrasolar Giant Planet with a stratosphere?
• Hot Super-Earths with Hydrogen Atmospheres: A Model Explaining Their Paradoxical Existence

Cited by in corpus (28)

• The nature and origins of sub-Neptune size planets
• A secondary atmosphere on the rocky exoplanet 55 Cancri e
• ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b
• No escaping helium from 55 Cnc e
• Dry or water world? How the water contents of inner sub-Neptunes constrain giant planet formation and the location of the water ice line
• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
• A detailed analysis of the Gl 486 planetary system
• Caught in the Act: Core-powered Mass-loss Predictions for Observing Atmospheric Escape
• Super-Earths and Earth-like Exoplanets
• JWST reveals a rapid and strong day side variability of 55 Cancri e
• A Near-Infrared Chemical Inventory of the Atmosphere of 55 Cancri e
• The PEPSI Exoplanet Transit Survey (PETS) I: Investigating the presence of a silicate atmosphere on the super-Earth 55 Cnc e
• A super-Earth and a mini-Neptune near the 2:1 MMR straddling the radius valley around the nearby mid-M dwarf TOI-2096
• VapoRock: Thermodynamics of vaporized silicate melts for modeling volcanic outgassing and magma ocean atmospheres
• High-Resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
• Interior dynamics of super-Earth 55 Cancri e
• Investigating the visible phase-curve variability of 55 Cnc e
• 55 Cancri e's occultation captured with CHEOPS
• The hot Neptune WASP-166 b with ESPRESSO III: A blue-shifted tentative water signal constrains the presence of clouds
• High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
• The Exosphere as a Boundary: Origin and Evolution of Airless Bodies in the Inner Solar System and Beyond Including Planets with Silicate Atmospheres
• Temperature inversions on hot super-Earths: the case of CN in nitrogen-rich atmospheres
• The sulphur species in hot rocky exoplanet atmospheres
• TESS and HARPS reveal two sub-Neptunes around TOI 1062
• Ground-based Atmospheric Characterization of Super-Earth L 98-59 d at High Spectral Resolution
• Diversity of Exoplanets
• GJ 238 b: A 0.57 Earth Radius Planet Orbiting an M2.5 Dwarf Star at 15.2 pc
• Day-side Fe I Emission, Day-Night Brightness Contrast and Phase Offset of the Exoplanet WASP-33b