Average Albedos of Close-in Super-Earths and Neptunes from Statistical Analysis of Long Cadence Kepler Secondary Eclipse Data

Abstract

We present the results of our work to determine the average albedo for small, close-in planets in the {\it Kepler} candidate catalog. We have adapted our method of averaging short cadence light curves of multiple Kepler planet candidates to long cadence data, in order to detect an average albedo for the group of candidates. Long cadence data exist for many more candidates than the short cadence, and so we separate the candidates into smaller radius bins than in our previous work: 1-2 Rearth, 2-4 Rearth, and 4-6 Rearth. We find that on average, all three groups appear darker than suggested by the short cadence result, but not as dark as many hot Jupiters. The average geometric albedos for the three groups are 0.11 $\pm$ 0.06, 0.05 $\pm$ 0.04, and 0.11 $\pm$ 0.08, respectively, for the case where heat is uniformly distributed about the planet. If heat redistribution is inefficient, the albedos are even lower, since there will be a greater thermal contribution to the total light from the planet. We confirm that newly-identified false positive Kepler Object of Interest (KOI) 1662.01 is indeed an eclipsing binary at twice the period listed in the planet candidate catalog. We also newly identify planet candidate KOI 4351.01 as an eclipsing binary, and we report a secondary eclipse measurement for Kepler-4b (KOI 7.01) of $\sim$ 7.50 ppm at a phase of $\sim$ 0.7, indicating that the planet is on an eccentric orbit.

9 pages of text plus 26 figures and 4 tables, accepted for publication in AJ

References in corpus (16)

• Detection of Thermal Emission from an Extrasolar Planet
• KEPLER's First Rocky Planet: Kepler-10b
• The Kepler Follow-Up Observation Program. I. A Catalog of Companions to Kepler Stars from High-Resolution Imaging
• Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
• Chemistry of Silicate Atmospheres of Evaporating Super-Earths
• Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry
• On the Absorption and Redistribution of Energy in Irradiated Planets
• Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths
• Atmospheric Characterization of the Hot Jupiter Kepler-13Ab
• Thermal Emission from Transiting Very-Hot Jupiters: Prospects for Ground-based Detection at Optical Wavelengths
• Low False-Positive Rate of Kepler Candidates Estimated From A Combination Of Spitzer And Follow-Up Observations
• Assessing the Effect of Stellar Companions from High-Resolution Imaging of Kepler Objects of Interest
• Kepler423b: a half-Jupiter mass planet transiting a very old solar-like star
• The Albedos of Kepler's Close-in super-Earths
• Discovery of the secondary eclipse of HAT-P-11 b
• Statistical Eclipses of Close-in Kepler Sub-Saturns

Cited by in corpus (9)

• Aerosols in Exoplanet Atmospheres
• Atmospheres of Rocky Exoplanets
• The Compositional Diversity of Low-Mass Exoplanets
• Multi-season optical modulation phased with the orbit of the super-Earth 55 Cnc e
• Probing Kepler's hottest small planets via homogeneous search and analysis of optical secondary eclipses and phase variations
• XO-7 b: A transiting hot Jupiter with a massive companion on a wide orbit
• A High Geometric Albedo for LTT9779b Points Towards a Metal-rich Atmosphere and Silicate Clouds
• The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys
• Kepler's Last Planet Discoveries: Two New Planets and One Single-Transit Candidate from K2 Campaign 19