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The Eccentricity Distribution of Short-period Planet Candidates Detected by Kepler in Occultation

Shabram, Megan and Demory, Brice-Olivier and Cisewski, Jessi and Ford, Eric B. and Rogers, Leslie (2016) The Eccentricity Distribution of Short-period Planet Candidates Detected by Kepler in Occultation. Astrophysical Journal, 820 (2). Art. No. 93. ISSN 0004-637X.

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We characterize the eccentricity distribution of a sample of ~50 short-period planet candidates using transit and occultation measurements from NASA's Kepler Mission. First, we evaluate the sensitivity of our hierarchical Bayesian modeling and test its robustness to model misspecification using simulated data. When analyzing actual data assuming a Rayleigh distribution for eccentricity, we find that the posterior mode for the dispersion parameter is σ =0.081 ± _(0.003)^(0.014). We find that a two-component Gaussian mixture model for e cos ω and e sin ω provides a better model than either a Rayleigh or Beta distribution. Based on our favored model, we find that ~90% of planet candidates in our sample come from a population with an eccentricity distribution characterized by a small dispersion (~0.01), and ~10% come from a population with a larger dispersion (~0.22). Finally, we investigate how the eccentricity distribution correlates with selected planet and host star parameters. We find evidence that suggests systems around higher metallicity stars and planet candidates with smaller radii come from a more complex eccentricity distribution.

Item Type:Article
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URLURL TypeDescription Paper
Demory, Brice-Olivier0000-0002-9355-5165
Ford, Eric B.0000-0001-6545-639X
Rogers, Leslie0000-0003-0638-3455
Additional Information:© 2016 American Astronomical Society. Received 2015 February 14; accepted 2015 September 20; published 2016 March 23. We thank the entire Kepler team for the many years of work that have proven so successful and was critical to this study. We acknowledge the SAMSI Bayesian Characterization of Extrasolar Populations working group for discussions that improved this manuscript. In particular, we thank Merlise Clyde, Darin Ragozzine, Thomas Loredo, David Hogg, Thomas Barclay, and Robert Wolpert for their valuable contributions to the project. This work was supported in part by the Pennsylvania State University's Center for Exoplanets and Habitable Worlds, NASA Kepler Participating Scientist Program awards NNX12AF73G and NNX14AN76G, and NASA Origins of Solar Systems awards NNX13AF61G and NNX14AI76G. This material was based upon work partially supported by the National Science Foundation under grant DMS-1127914 to the Statistical and Applied Mathematical Sciences Institute (SAMSI). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The authors acknowledge the Institute for CyberScience at The Pennsylvania State University for providing advanced computing resources and services that have contributed to the research results reported in this paper (, in particular Hoofar Pourzand and William Brouwer. The authors acknowledge the University of Florida Research Computing ( for providing computational resources and support that have contributed to the research results reported in this publication. Some/all 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 research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. We also acknowledge Dan Foreman Mackey's open source code for which we adapted for Figure 5. Facility: Kepler - The Kepler Mission
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Pennsylvania State UniversityUNSPECIFIED
Subject Keywords:methods: statistical; planets and satellites: dynamical evolution and stability; planets and satellites: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20160510-084600260
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Official Citation:Megan Shabram et al 2016 ApJ 820 93
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66837
Deposited By: Ruth Sustaita
Deposited On:10 May 2016 16:41
Last Modified:28 Oct 2019 23:56

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