Confirming Variability in the Secondary Eclipse Depth of the Super-Earth 55 Cancri e

Abstract

We present a reanalysis of five transit and eight eclipse observations of the ultra-short period super-Earth 55 Cancri e observed using the Spitzer Space Telescope during 2011-2013. We use pixel-level decorrelation to derive accurate transit and eclipse depths from the Spitzer data, and we perform an extensive error analysis. We focus on determining possible variability in the eclipse data, as was reported in Demory et al. 2016a. From the transit data, we determine updated orbital parameters, yielding T0 = 2455733.0037 $\pm$ 0.0002, P = 0.7365454 $\pm$ 0.0000003 days, i = 83.5 $\pm$ 1.3 degrees, and $R_p$ = 1.89 $\pm$ 0.05 $R_{\oplus }$. Our transit results are consistent with a constant depth, and we conclude that they are not variable. We find a significant amount of variability between the eight eclipse observations, and confirm agreement with Demory et al. 2016a through a correlation analysis. We convert the eclipse measurements to brightness temperatures, and generate and discuss several heuristic models that explain the evolution of the planet's eclipse depth versus time. The eclipses are best modeled by a year-to-year variability model, but variability on shorter timescales cannot be ruled out. The derived range of brightness temperatures can be achieved by a dark planet with inefficient heat redistribution intermittently covered over a large fraction of the sub-stellar hemisphere by reflective grains, possibly indicating volcanic activity or cloud variability. This time-variable system should be observable with future space missions, both planned (JWST) and proposed (i.e. ARIEL).

arXiv comment16 pages, 12 figures, accepted for publication in AJ; fixed affiliation for A. Mandell

References in corpus (41)

• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• The James Webb Space Telescope
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• Detection of Thermal Emission from an Extrasolar Planet
• Quantifying the Uncertainty in the Orbits of Extrasolar Planets
• Detection of a NEPTUNE-mass planet in the ${\rho }^1$ Cancri system using the Hobby-Eberly Telescope
• 3.6 and 4.5 Micron Phase Curves and Evidence for Non-Equilibrium Chemistry in the Atmosphere of Extrasolar Planet HD 189733b
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• PandExo: A Community Tool for Transiting Exoplanet Science with JWST & HST
• A map of the large day-night temperature gradient of a super-Earth exoplanet
• Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation
• A Super-Earth Transiting a Naked-Eye Star
• Five Planets Orbiting 55 Cancri
• EVEREST: Pixel Level Decorrelation of K2 Light curves
• Composition and fate of short-period super-Earths: The case of CoRoT-7b
• Chemistry of Silicate Atmospheres of Evaporating Super-Earths
• Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
• Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b
• Transit and Eclipse Analyses of Exoplanet HD 149026b Using BLISS Mapping
• Born Dry in the Photo-Evaporation Desert: Kepler's Ultra-Short-Period Planets Formed Water-Poor
• Variability in the super-Earth 55 Cnc e
• 3.6 and 4.5 $\mu$m $Spitzer$ Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b
• Theoretical Spectra of Terrestrial Exoplanet Surfaces
• 55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth
• Detecting planetary geochemical cycles on exoplanets: Atmospheric signatures and the case of SO2
• The 55 Cancri Planetary System: Fully Self-Consistent N-body Constraints and a Dynamical Analysis
• Repeatability and Accuracy of Exoplanet Eclipse Depths Measured with Post-Cryogenic Spitzer
• Ground-based detection of thermal emission from the exoplanet WASP-19b
• HST hot-Jupiter transmission spectral survey: Clear skies for cool Saturn WASP-39b
• Mercury-T: A new code to study tidally evolving multi-planet systems. Applications to Kepler-62
• Revisiting rho 1 Cancri e: A New Mass Determination Of The Transiting super-Earth
• Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra
• Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets
• Dynamical Constraints on the Core Mass of Hot Jupiter HAT-P-13b
• Enhanced models for stellar Doppler noise reveal hints of a 13-year activity cycle of 55 Cancri
• Tidal dissipation in a homogeneous spherical body. II. Three examples: Mercury, Io, and Kepler-10 b
• A Search for Additional Bodies in the GJ 1132 Planetary System from 21 Ground-based Transits and a 100 Hour Spitzer Campaign
• Spitzer Secondary Eclipse Depths with Multiple Intrapixel Sensitivity Correction Methods: Observations of WASP-13b, WASP-15b, WASP-16b, WASP-62b, and HAT-P-22b
• Two NIRCam channels are Better than One: How JWST Can Do More Science with NIRCam's Short-Wavelength Dispersed Hartmann Sensor
• ACME Stellar Spectra. I. Absolutely Calibrated, Mostly Empirical Flux Densities of 55 Cancri and its Transiting Planet 55 Cancri e
• Slitless spectroscopy with the James Webb Space Telescope Near-Infrared Camera (JWST NIRCam)

Cited by in corpus (29)

• A secondary atmosphere on the rocky exoplanet 55 Cancri e
• Statistical Characterization of Hot Jupiter Atmospheres using Spitzer's Secondary Eclipses
• GJ 1252b: A Hot Terrestrial Super-Earth With No Atmosphere
• K2 and Spitzer phase curves of the rocky ultra-short-period planet K2-141 b hint at a tenuous rock vapor atmosphere
• Temporal Variability in Hot Jupiter Atmospheres
• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
• Lava Worlds: From Early Earth to Exoplanets
• JWST reveals a rapid and strong day side variability of 55 Cancri e
• An Unusual Transmission Spectrum for the Sub-Saturn KELT-11b Suggestive of a Sub-Solar Water Abundance
• 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
• Spitzer Detection of the Transiting Jupiter-analog Exoplanet Kepler-167e
• Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e
• Investigating the visible phase-curve variability of 55 Cnc e
• 55 Cancri e's occultation captured with CHEOPS
• Reassessing the Evidence for Time Variability in the Atmosphere of the Exoplanet HAT-P-7 b
• Weak evidence for variable occultation depth of 55 Cnc e with TESS
• Emergent Spectral Fluxes of Hot Jupiters: an Abrupt Rise in Day Side Brightness Temperature Under Strong Irradiation
• How to Characterize the Atmosphere of a Transiting Exoplanet
• The Exosphere as a Boundary: Origin and Evolution of Airless Bodies in the Inner Solar System and Beyond Including Planets with Silicate Atmospheres
• Hot Super-Earths with Hydrogen Atmospheres: A Model Explaining Their Paradoxical Existence
• MIRECLE: Science Yield for a Mid-IR Explorer-Class Mission to Study Non-Transiting Rocky Planets Orbiting the Nearest M-Stars Using Planetary Infrared Excess
• Atmospheric Characterization via Broadband Color Filters on the PLAnetary Transits and Oscillations of stars (PLATO) Mission
• Extreme Weather Variability on Hot Rocky Exoplanet 55 Cancri e Explained by Magma Temperature-Cloud Feedback
• Atmospheric characterization of hot Jupiters using hierarchical models of Spitzer observations
• A general polarimetric model for transiting and non-transiting ringed exoplanets
• Diversity of Exoplanets
• Hot Rocks Survey V: Secondary Eclipse Photometry of GJ 3473 b with JWST/MIRI
• General Circulation Model Errors are Variable across Exoclimate Parameter Spaces