Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e

Abstract

Context. 55 Cnc e is a transiting super-Earth orbiting a solar-like star with an orbital period of 17.7 hours. In 2011, using the MOST space telescope, a quasi-sinusoidal modulation in flux was detected with the same period as the planetary orbit. The amplitude of this modulation was too large to be explained as the change in light reflected or emitted by the planet. Aims. The MOST telescope continued to observe 55 Cnc e for a few weeks per year over five years, covering 143 individual transits. This paper presents the analysis of the observed phase modulation throughout these observations and a search for the secondary eclipse of the planet. Methods. The most important source of systematic noise in MOST data is due to stray-light reflected from the Earth, which is modulated with both the orbital period of the satellite and the Earth's rotation period. We present a new technique to deal with this source of noise, which we combined with standard detrending procedures for MOST data. We then performed Markov Chain Monte Carlo analyses of the detrended light curves, modeling the planetary transit and phase modulation. Results. We find phase modulations similar to those seen in 2011 in most of the subsequent years; however, the amplitude and phase of maximum light are seen to vary from 113 to 28 ppm and from 0.1 to 3.8 rad. The secondary eclipse is not detected, but we constrain the geometric albedo of the planet to less than 0.47 (2$\sigma$). Conclusions. While we cannot identify a single origin of the observed optical modulation, we propose a few possible scenarios. Those include star-planet interaction or the presence of a transiting circumstellar torus of dust. However, a detailed interpretation of these observations is limited by their photometric precision. Additional observations at optical wavelengths could contribute to uncovering the underlying physical processes.

arXiv commentAccepted for publication in Astronomy and Astrophysics

References in corpus (72)

• Analytic Lightcurves for Planetary Transit Searches
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The false positive rate of Kepler and the occurrence of planets
• Prevalence of Earth-size planets orbiting Sun-like stars
• The evaporation valley in the Kepler planets
• The effect of red noise on planetary transit detection
• KEPLER's First Rocky Planet: Kepler-10b
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths
• A Framework for Quantifying the Degeneracies of Exoplanet Interior Compositions
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• A map of the large day-night temperature gradient of a super-Earth exoplanet
• Migration then assembly: Formation of Neptune mass planets inside 1 AU
• Compositional imprints in density-distance-time: a rocky composition for close-in low-mass exoplanets from the location of the valley of evaporation
• A Super-Earth Transiting a Naked-Eye Star
• Formation and Structure of Low Density Exo-Neptunes
• Characterization of exoplanets from their formation II: The planetary mass-radius relationship
• Five Planets Orbiting 55 Cancri
• A diagram for the evaporation status of extrasolar planets
• CHEOPS: A Transit Photometry Mission for ESA's Small Mission Programme
• Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres
• Detection of an atmosphere around the super-Earth 55 Cancri e
• Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
• The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry of HD 209458
• Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry
• An Upper Limit on the Albedo of HD 209458b: Direct Imaging Photometry with the MOST Satellite
• The high albedo of the hot Jupiter Kepler-7b
• Hint of a transiting extended atmosphere on 55 Cancri b
• Variability in the super-Earth 55 Cnc e
• A comprehensive study of Kepler phase curves and secondary eclipses -- temperatures and albedos of confirmed Kepler giant planets
• The HARPS-N Rocky Planet Search I. HD219134b: A transiting rocky planet in a multi-planet system at 6.5 pc from the Sun
• Atmosphere-interior exchange on hot rocky exoplanets
• On Correlated-noise Analyses Applied To Exoplanet Light Curves
• The thermal emission of the young and massive planet CoRoT-2b at 4.5 and 8 microns
• A grid of upper atmosphere models for 1--40 MEARTH planets: application to CoRoT-7 b and HD219134 b,c
• Jupiter's Decisive Role in the Inner Solar System's Early Evolution
• The 55 Cnc system reassessed
• 55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth
• TESS's first planet: a super-Earth transiting the naked-eye star $\pi$ Mensae
• Mass-loss rates for transiting exoplanets
• Magnetic games between a planet and its host star: the key role of topology
• Improved precision on the radius of the nearby super-Earth 55 Cnc e
• MOST detects variability on tau Bootis possibly induced by its planetary companion
• A new class of Super-Earths formed from high-temperature condensates: HD219134 b, 55 Cnc e, WASP-47 e
• MOST detects transits of HD 97658b, a warm, likely volatile-rich super-Earth
• Evidence for a lost population of close-in exoplanets
• A Case for an Atmosphere on Super-Earth 55 Cancri e
• Search for an exosphere in sodium and calcium in the transmission spectrum of exoplanet 55 Cancri e
• The orbital phases and secondary transit of Kepler-10b - A physical interpretation based on the Lava-ocean planet model -
• A probable planetary companion to HD 39091 from the Anglo-Australian Planet Search
• Star-planet magnetic interaction and activity in late-type stars with close-in planets
• Lifetimes and Emergence/Decay Rates of Star Spots on Solar-type Stars Estimated by Kepler Data in Comparison with Those of Sunspots
• A Six-Planet System Orbiting HD 219134
• Coordinated X-ray and Optical observations of Star-Planet Interaction in HD 17156
• A correlation between host star activity and planet mass for close-in extrasolar planets?
• Jovian Dust Streams: A monitor of Io's volcanic plume activity
• Signs of strong Na and K absorption in the transmission spectrum of WASP-103b
• CoRoT-2a magnetic activity: hints for possible star-planet interaction
• The Albedos of Kepler's Close-in super-Earths
• Confirming Variability in the Secondary Eclipse Depth of the Super-Earth 55 Cancri e
• Ground-Based Transit Observations of the Super-Earth 55 Cnc e
• Differential rotation of the active G5V star Kappa1 Ceti: Photometry from the MOST satellite
• Evidence of magnetic star-planet interactions in the HD 189733 system from orbitally-phased Ca II K variations
• Chasing star-planet magnetic interactions: the case of Kepler-78
• Evidence for Reflected Light from the Most Eccentric Exoplanet Known
• Average Albedos of Close-in Super-Earths and Neptunes from Statistical Analysis of Long Cadence Kepler Secondary Eclipse Data
• Kepler's Dark Worlds: a Low Albedo for an Ensemble of Neptunian and Terran Exoplanets
• ACME Stellar Spectra. I. Absolutely Calibrated, Mostly Empirical Flux Densities of 55 Cancri and its Transiting Planet 55 Cancri e
• Planetary Phase Variations of the 55 Cancri System

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• K2 and Spitzer phase curves of the rocky ultra-short-period planet K2-141 b hint at a tenuous rock vapor atmosphere
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• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
• Lava Worlds: From Early Earth to Exoplanets
• Demonstrating high-precision photometry with a CubeSat: ASTERIA observations of 55 Cancri e
• $TESS$ Phase Curve of the Hot Jupiter WASP-19b
• JWST reveals a rapid and strong day side variability of 55 Cancri e
• Atmospheric compositions and observability of nitrogen dominated ultra-short period super-Earths
• Revisiting the Iconic Spitzer Phase Curve of 55 Cancri e: Hotter Dayside, Cooler Nightside and Smaller Phase Offset
• Interior dynamics of super-Earth 55 Cancri e
• Possible Atmospheric Diversity of Low Mass Exoplanets, some Central Aspects
• Investigating the visible phase-curve variability of 55 Cnc e
• 55 Cancri e's occultation captured with CHEOPS
• Weak evidence for variable occultation depth of 55 Cnc e with TESS
• Characterising the Atmosphere of 55 Cancri e: 1D Forward Model Grid for Current and Future JWST Observations
• Extreme Weather Variability on Hot Rocky Exoplanet 55 Cancri e Explained by Magma Temperature-Cloud Feedback