Multiple Kepler "Terrestrial" Exoplanets are Really SuperEarths and Mini Neptunes

REVISION OF EARTH-SIZED KEPLER PLANET CANDIDATE PROPERTIES WITH HIGH-RESOLUTION IMAGING BY THE HUBBLE SPACE TELESCOPE

Authors:

Cartier et al

Abstract:

We present the results of our Hubble Space Telescope program and describe how our analysis methods were used to re-evaluate the habitability of some of the most interesting Kepler planet candidates. Our program observed 22 Kepler Object of Interest (KOI) host stars, several of which were found to be multiple star systems unresolved by Kepler. We use our high-resolution imaging to spatially resolve the stellar multiplicity of Kepler-296, KOI-2626, and KOI-3049, and develop a conversion to the Kepler photometry (Kp) from the F555W and F775W filters on WFC3/UVIS. The binary system Kepler-296 (five planets) has a projected separation of $0\buildrel{\prime\prime}\over{.} 217$ (80 AU); KOI-2626 (one planet candidate) is a triple star system with a projected separation of $0\buildrel{\prime\prime}\over{.} 201$ (70 AU) between the primary and secondary components and $0\buildrel{\prime\prime}\over{.} 161$ (55 AU) between the primary and tertiary; and the binary system KOI-3049 (one planet candidate) has a projected separation of $0\buildrel{\prime\prime}\over{.} 464$ (225 AU). We use our measured photometry to fit the separated stellar components to the latest Victoria–Regina Stellar Models with synthetic photometry to conclude that the systems are coeval. The components of the three systems range from mid-K dwarf to mid-M dwarf spectral types.We solved for the planetary properties of each system analytically and via an MCMC algorithm using our independent stellar parameters. The planets range from $\sim 1.6\;\;{\rm to}\;\sim 4.2\;{{R}_{\oplus }}$, mostly Super Earths and mini-Neptunes. As a result of the stellar multiplicity, some planets previously in the Habitable Zone are, in fact, not, and other planets may be habitable depending on their assumed stellar host.