Poster Abstracts - Kepler - NASA

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POSTER ABSTRACTSP0301. POSTER SESSION IExoplanet Migration and the Distribution of Period Ratios in Multiple Planet Systems KatherineM. Deck 1 and Matthew J. Holman 2 , 1 Massachussetts Institute of Technology, Physics Department,kdeck@mit.edu, 2 Harvard-Smithsonian Center for Astrophysics, mholman@cfa.harvard.eduCapture into resonance is a natural consequenceof convergent migration in multiple planetsystems [1,2,3,4]. As planets migrate, the ratiosof orbital periods within the system slowlychange. When they approach a commensurability,there is some probability of capture into resonance.An interesting observational result from theKepler data is that planets in multiple planet systemsfound near first order mean motion resonancestend to be grouped outside of the nominalresonance value [5]. If this result holds as moreplanets are discovered, it could constrain planetarymigration theories.We are studying the process of captureinto the 2:1 resonance in particular, as period ratiosnear two are common among the systems discovered[5]. By numerically evolving a planetarysystem with two planets, according to the usualHamiltonian gravitational dynamics as well as avery general migration mechanism, we confirmthat capture into the 2:1 resonance can occur andshow that period ratios greater than two can beachieved for specific dissipation rates. We areexploring whether or not these rates are physical.In addition, we are also studying the evolutionsemi-analytically by modeling the system as beinggoverned by an adiabatically changing Hamiltonian.This will allow us to better understand thedistribution of period ratios that result from convergentmigration, capture into resonance, andsubsequent termination of migration.[1] Goldreich, P. 1965, MNRAS, 130, 159[2] Lee, M. H., and Peale, S. J., 2002, ApJ,567, 596.[3] Lee, M. H., 2004, ApJ, 611, 517[4] C. Beaugé, S. Ferraz-Mello & T.A. Michtchenko,2003, ApJ, 593, 1124-1133[5] JJ Lissauer et al, November 2011, ApJs, &arXiv:1102.0543v41562011 Kepler Science Conference - NASA Ames Research Center
POSTER ABSTRACTSP0302. POSTER SESSION IPredicting Planets in Kepler Candidate Multi-Planet Systems. J. Fang 1 and J. L. Margot 2 , 1 Department of Physicsand Astronomy, 430 Portola Plaza, Box 951547, University of California, Los Angeles, CA 90095, USA, e-mail:fang@astro.ucla.edu, 2 University of California, Los Angeles, e-mail: jlm@astro.ucla.eduIntroduction: Early studies of extrasolar planetarysystems showed residual velocity trends in Keplerianorbit fits to radial velocity data [1-5], suggesting thatthese systems may harbor additional, yet-undetectedcompanions. Many of these systems were later discoveredto host additional planet(s). In more recent years,the study and prediction of undiscovered planets havebeen boosted by long-term N-body simulations. Thesenumerical investigations searched for stability zones inmulti-planet systems by integrating many test bodies,which were injected into empty regions betweenknown planets [6-10]. In the case of exoplanet HD74156d [11], this Saturn-mass planet was first predictedthrough numerical simulations showing a stableregion between planets b and c [8], and then later discovered[12]. This successful prediction was motivatedby the “packed planetary systems” (PPS) hypothesis.The PPS hypothesis is the idea that planetary systemsare formed “dynamically full” and filled to capacity,and any additional planets will cause the system tobe unstable [7-8,13-14]. Consequently, planetary systemswith stable stability zones between the innermostand outermost planets are suggestive of additional, yetundetectedplanets. The orbital properties of predictedplanets can be identified through long-term numericalsimulations.In the present study, we apply the PPS hypothesisto multi-planet candidate systems discovered by theKepler mission [15]. Given the high frequency ofpacking found in known planetary systems, we seek totest the PPS hypothesis and predict additional planetsin Kepler candidate multi-planet systems through analyticaland numerical methods.Methods: We use publicly available Kepler datacovering the first four and a half months of observations[16]. One-third of the planetary candidates in thisdataset are hosted in a total of 170 multi-planet systems[17]. Of these systems, we analytically calculatethe Hill stability of all adjacent planet pairs to discernthe extent of packing in the systems. Fulfillment orover-fulfillment of the Hill stability criterion, implyingthat the considered planet pair is not on the verge ofinstability, suggests the presence of additional planets.We find that many of the systems are packed and wefocus on
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Poster Abstracts - Kepler - NASA

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