Weak evidence for variable occultation depth of 55 Cnc e with TESS

Abstract

55 Cnc e is in a 0.73 day orbit transiting a Sun-like star. It has been observed that the occultation depth of this Super-Earth, with a mass of 8$M_{⨁}$ and radius of 2$R_{⨁}$, changes significantly over time at mid-infrared wavelengths. Observations with Spitzer measured a change in its day-side brightness temperature of 1200 K, possibly driven by volcanic activity, magnetic star-planet interaction, or the presence of a circumstellar torus of dust. Previous evidence for the variability in occultation was in the infrared range. Here we aim to explore if the variability exists also in the optical. TESS observed 55 Cnc during sectors 21, 44 and 46. We carefully detrend the data and fit a transit and occultation model for each sector in a Markov Chain Monte Carlo routine. In a later stage we use the Leave-One-Out Cross-Validation statistic to compare with a model of constant occultation for the complete set and a model with no occultation. We report an occultation depth of 8$\pm$2.5 ppm for the complete set of TESS observations. In particular, we measured a depth of 15$\pm$4 ppm for sector 21, while for sector 44 we detect no occultation. In sector 46 we measure a weak occultation of 8$\pm$5 ppm. The occultation depth varies from one sector to the next between 1.6 and 3.4 $\sigma$ significance. We derive the possible contribution on reflected light and thermal emission, setting an upper limit on the geometric albedo. Based on our model comparison the presence of an occultation is favoured considerably over no occultation, where the model with varying occultation across sectors takes most of the statistical weight. Our analysis confirms a detection of the occultation in TESS. Moreover, our results weakly lean towards a varying occultation depth between each sector, while the transit depth is constant across visits.

arXiv comment9 pages, 9 figures, accepted for publication on A&A

References in corpus (42)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Gaia mission
• Practical Bayesian model evaluation using leave-one-out cross-validation and WAIC
• The Transiting Exoplanet Survey Satellite
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• The Spitzer Space Telescope Mission
• Analytic Lightcurves for Planetary Transit Searches
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• Understanding the Lomb-Scargle Periodogram
• batman: BAsic Transit Model cAlculatioN in Python
• Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws
• astroquery: An Astronomical Web-Querying Package in Python
• Using stacking to average Bayesian predictive distributions
• Detection of a NEPTUNE-mass planet in the ${\rho }^1$ Cancri system using the Hobby-Eberly Telescope
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• STARRY: Analytic Occultation Light Curves
• Limb and gravity-darkening coefficients for the TESS satellite at several metallicities, surface gravities, and microturbulent velocities
• A map of the large day-night temperature gradient of a super-Earth exoplanet
• A Super-Earth Transiting a Naked-Eye Star
• Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1
• Wotan: Comprehensive time-series de-trending in Python
• Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548
• Pareto Smoothed Importance Sampling
• Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
• Analytic Planetary Transit Light Curves and Derivatives for Stars with Polynomial Limb Darkening
• 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
• The K2-ESPRINT Project. I. Discovery of the Disintegrating Rocky Planet K2-22b with a Cometary Head and Leading Tail
• 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
• Statistical Characterization of Hot Jupiter Atmospheres using Spitzer's Secondary Eclipses
• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
• Confirming Variability in the Secondary Eclipse Depth of the Super-Earth 55 Cancri e
• Low albedos of hot to ultra-hot Jupiters in the optical to near-infrared transition regime
• Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e
• Analytic solutions to the maximum and average exoplanet transit depth for common stellar limb darkening laws
• The TESS Phase Curve of KELT-1b Suggests a High Dayside Albedo
• New MOST Photometry of the 55 Cancri System

Cited by in corpus (12)

• A secondary atmosphere on the rocky exoplanet 55 Cancri e
• On the Application of Bayesian Leave-One-Out Cross-Validation to Exoplanet Atmospheric Analysis
• JWST reveals a rapid and strong day side variability of 55 Cancri e
• 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
• Investigating the visible phase-curve variability of 55 Cnc e
• Hot Rocks Survey II: The thermal emission of TOI-1468 b reveals a hot bare rock
• 55 Cancri e's occultation captured with CHEOPS
• JWST NIRCam Defocused Imaging: Photometric Stability Performance and How it Can Sense Mirror Tilts
• 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
• A general polarimetric model for transiting and non-transiting ringed exoplanets