Architecture and Dynamics of Kepler's Candidate Multiple Transiting Planet Systems

Creators: Lissauer, Jack J.; Ragozzine, Darin; Fabrycky, Daniel C.; Steffen, Jason H.; Ford, Eric B.; Jenkins, Jon M.; Shporer, Avi; Holman, Matthew J.; Rowe, Jason F.; Quintana, Elisa V.; Batalha, Natalie M.; Borucki, William J.; Bryson, Stephen T.; Caldwell, Douglas A.; Carter, Joshua A.; Ciardi, David; Dunham, Edward W.; Fortney, Jonathan J.; Gautier, Thomas N., III; Howell, Stephen B.; Koch, David G.; Latham, David W.; Marcy, Geoffrey W.; Morehead, Robert C.; Sasselov, Dimitar

Abstract

About one-third of the ~1200 transiting planet candidates detected in the first four months of Kepler data are members of multiple candidate systems. There are 115 target stars with two candidate transiting planets, 45 with three, 8 with four, and 1 each with five and six. We characterize the dynamical properties of these candidate multi-planet systems. The distribution of observed period ratios shows that the vast majority of candidate pairs are neither in nor near low-order mean-motion resonances. Nonetheless, there are small but statistically significant excesses of candidate pairs both in resonance and spaced slightly too far apart to be in resonance, particularly near the 2:1 resonance. We find that virtually all candidate systems are stable, as tested by numerical integrations that assume a nominal mass-radius relationship. Several considerations strongly suggest that the vast majority of these multi-candidate systems are true planetary systems. Using the observed multiplicity frequencies, we find that a single population of planetary systems that matches the higher multiplicities underpredicts the number of singly transiting systems. We provide constraints on the true multiplicity and mutual inclination distribution of the multi-candidate systems, revealing a population of systems with multiple super-Earth-size and Neptune-size planets with low to moderate mutual inclinations.

Additional Information

© 2011 American Astronomical Society. Received 2011 February 24; accepted 2011 July 20; published 2011 October 13. Kepler was competitively selected as NASA's tenth Discovery mission. Funding for this mission is provided by NASA's Science Mission Directorate. The authors thank the many people who gave so generously of their time to make the Kepler mission a success. D.C.F. and J.A.C. acknowledge NASA support through Hubble Fellowship grants HF-51272.01-A and HF-51267.01-A, respectively, awarded by STScI, operated by AURA under contract NAS 5-26555. We thank Bill Cochran, Avi Loeb, Hanno Rein, Subo Dong, and Bill Welsh for valuable discussions and Kevin Zahnle, Tom Greene, Andrew Youdin, and an anonymous reviewer for constructive comments on the manuscript. Numerical integrations to test the stability of nominal planetary systems were run on the supercomputer Pleiades at University of California, Santa Cruz. Note added in proof. A reanalysis of the lightcurve of KOI-191 reveals that the period of KOI-191.04 is twice as large as the value reported in B11; the corrected period is 38.65159 ± 0.00119 days. KOI-191.04 is the outermost of its target's four candidates. Integrations of this system using the B11 period and nominal masses went unstable (Section 4), although the proximity of the outer two candidates to the 5:4 mean motion period commensurability allowed for the possibility of protection via resonance (Section 5.4). With the revised period of the outer candidate, the system is stable for nominal masses. A similar factor of two period error occurred for KOI-787.02; the revised period implies that this candidate is not in the 9:7 resonance with KOI-787.01 (Section 5.6).

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