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.

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

References in corpus (9)

• Array Programming with NumPy
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• astroquery: An Astronomical Web-Querying Package in Python
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc 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

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