Investigating the visible phase-curve variability of 55 Cnc e

Abstract

55 Cnc e is an ultra-short period super-Earth transiting a Sun-like star. Previous observations in the optical range detected a time-variable flux modulation that is phased with the planetary orbital period, whose amplitude is too large to be explained by reflected light and thermal emission alone. The goal of the study is to investigate the origin of the variability and timescale of the phase-curve modulation in 55 Cnc e. To this end, we used the CHaracterising ExOPlanet Satellite (CHEOPS), whose exquisite photometric precision provides an opportunity to characterise minute changes in the phase curve from one orbit to the next. CHEOPS observed 29 individual visits of 55 Cnc e between March 2020 and February 2022. Based on these observations, we investigated the different processes that could be at the origin of the observed modulation. In particular, we built a toy model to assess whether a circumstellar torus of dust driven by radiation pressure and gravity might match the observed flux variability timescale. We find that the phase-curve amplitude and peak offset of 55 Cnc e do vary between visits. The sublimation timescales of selected dust species reveal that silicates expected in an Earth-like mantle would not survive long enough to explain the observed phase-curve modulation. We find that silicon carbide, quartz, and graphite are plausible candidates for the circumstellar torus composition because their sublimation timescales are long. The extensive CHEOPS observations confirm that the phase-curve amplitude and offset vary in time.We find that dust could provide the grey opacity source required to match the observations. However, the data at hand do not provide evidence that circumstellar material with a variable grain mass per unit area causes the observed variability. Future observations with the James Webb Space Telescope promise exciting insights into this iconic super-Earth.

27 pages, 22 figures. Accepted for publication on A&A

References in corpus (33)

• Array Programming with NumPy
• astroquery: An Astronomical Web-Querying Package in Python
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• Five Planets Orbiting 55 Cancri
• Six transiting planets and a chain of Laplace resonances in TOI-178
• Classification of magnetized star--planet interactions: bow shocks, tails, and inspiraling flows
• Variability in the Atmosphere of the Hot Giant Planet HAT-P-7 b
• Hot Jupiters and stellar magnetic activity
• The search for radio emission from the exoplanetary systems 55 Cancri, $\upsilon$ Andromedae, and $\tau$ Boötis using LOFAR beam-formed observations
• A Semi-Analytical Model of Visible-Wavelength Phase Curves of Exoplanets and Applications to Kepler-7 b and Kepler-10 b
• Transit detection of the long-period volatile-rich super-Earth ${\nu }^2$ Lupi d with $CHEOPS$
• CHEOPS observations of the HD 108236 planetary system: A fifth planet, improved ephemerides, and planetary radii
• A Case for an Atmosphere on Super-Earth 55 Cancri e
• The atmosphere and architecture of WASP-189 b probed by its CHEOPS phase curve
• Dusty tails of evaporating exoplanets. I. Constraints on the dust composition
• A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
• Assessing magnetic torques and energy fluxes in close-in star-planet systems
• No escaping helium from 55 Cnc e
• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
• CHEOPS geometric albedo of the hot Jupiter HD 209458b
• Alkaline Exospheres of Exoplanet Systems: Evaporative Transmission Spectra
• Arid or Cloudy: Characterizing the Atmosphere of the super-Earth 55 Cancri e using High-Resolution Spectroscopy
• Cloud formation in metal-rich atmospheres of hot super-Earths like 55 Cnc e and CoRot7b
• Dusty tails of evaporating exoplanets. II. Physical modelling of the KIC 12557548b light curve
• 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
• Revisiting the Iconic Spitzer Phase Curve of 55 Cancri e: Hotter Dayside, Cooler Nightside and Smaller Phase Offset
• The stable climate of KELT-9b
• Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e
• HORuS transmission spectroscopy of 55 Cnc e
• Analytic solutions to the maximum and average exoplanet transit depth for common stellar limb darkening laws
• MOVES V. Modelling star-planet magnetic interactions of HD 189733
• Reassessing the Evidence for Time Variability in the Atmosphere of the Exoplanet HAT-P-7 b

Cited by in corpus (3)

• A secondary atmosphere on the rocky exoplanet 55 Cancri e
• Interior dynamics of super-Earth 55 Cancri e
• Hot Rocks Survey II: The thermal emission of TOI-1468 b reveals a hot bare rock