Revision of Earth-sized Kepler Planet Candidate Properties with High-resolution Imaging by the Hubble Space Telescope

Creators: Cartier, Kimberly M. S.; Gilliland, Ronald L.; Wright, Jason T.; Ciardi, David R.

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."217 (80 AU); KOI-2626 (one planet candidate) is a triple star system with a projected separation of 0."201(70 AU) between the primary and secondary components and 0."161 (55 AU) between the primary and tertiary; and the binary system KOI-3049 (one planet candidate) has a projected separation of 0."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 ~ 1.6 to ~ 4.2 R_☉, 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.

Additional Information

© 2015 American Astronomical Society. Received 2014 July 3; accepted 2015 March 5; published 2015 May 6. K.M.S.C. performed analyses found in Sections 2–4 and discussion in Sections 1, 5, and 6. R.L.G. contributed analysis to Sections 3.1 and 3.4 as well as overall guidance and direction for this work and the companion paper Gilliland et al. (2015). J.T.W. contributed to Sections 1 and 6, and valuable discussion and advice regarding isochrone use. D.R.C. contributed Keck AO K-band data to Section 3.6 and provided discussion on KOI-2626. K.M.S.C. and R.L.G. have been partially supported through grant HST-GO-12893.01 A from STScI. We thank Don VandenBerg for permitting use of the latest Victoria–Regina Stellar Models before publication. We also thank Sharon X. Wang for discussion on error analysis for our isochrone fitting. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This paper makes use of data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. We gratefully acknowledge the use of SOA/NASA ADS, NASA, and STScI resources. Facilities: HST (WFC3), Kepler.

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Submitted - 1407.1057v3.pdf

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