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dc.contributor.authorHwang, Jason A.
dc.contributor.authorSteffen, Jason H.
dc.contributor.authorLombardi, James C., Jr. (Jamie)
dc.contributor.authorRasio, Frederic A.
dc.identifier.citationHwang, J.A., Steffen, J.H., Lombardi, J.C., Jr., Rasio, F.A. (2017) Dynamics and collisional evolution of closely packed planetary systems. MNRAS 470(4): 4145-4162. doi: 10.1093/mnras/stx1379en_US
dc.description.abstractHigh-multiplicity Kepler systems (referred to as Kepler multis) are often tightly packed and may be on the verge of instability. Many systems of this type could have experienced past instabilities, where the compact orbits and often low densities make physical collisions likely outcomes. We use numerical simulations to study the dynamical instabilities and planet-planet interactions in a synthetically generated sample of closely packed, high-multiplicity systems. We focus specifically on systems resembling Kepler-11, a Kepler multi with six planets, and run a suite of dynamical integrations, sampling the initial orbital parameters around the nominal values reported in Lissauer et al. (2011a), finding that most of the realizations are unstable, resulting in orbit crossings and, eventually, collisions and mergers. We study in detail the dependence of stability on the orbital parameters of the planets and planet-pair characteristics to identify possible precursors to instability, compare the systems that emerge from dynamical instabilities to the observed Kepler sample (after applying observational corrections), and propose possible observable signatures of these instabilities. We examine the characteristics of each planet-planet collision, categorizing collisions by the degree of contact and collision energy, and find that grazing collisions are more common than direct impacts. Since the structure of many planets found in Kepler multis is such that the mass is dominated by a rocky core, but the volume is dominated by a low-density gaseous envelope, the sticky-sphere approximation may not be valid, and we present hydrodynamic calculations of planet-planet collisions clearly deviating from this approximation. Finally, we rerun a subset of our dynamical calculations using instead a modified prescription to handle collisions, finding, in general, higher multiplicity remnant systems.en_US
dc.description.sponsorshipNASA / Kepler Participating Scientist Program / Lindheimer Fellowship at Northwestern University / NSF / Office for Research and Northwester University Information Technology / Office of the Provosten_US
dc.publisherOxford Academicen_US
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen_US
dc.rightsThis article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017. Hwang, LA (reprint author) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.en_US
dc.subjectequation of stateen_US
dc.subjectmethods: numericalen_US
dc.subjectplanets and satellites: dynamical evolution and stabilityen_US
dc.subjectstars: individual: (Kepler-11)en_US
dc.subjectsmoothed particle hydrodynamicsen_US
dc.subjectterrestrial planetsen_US
dc.subjectextrasolar planetsen_US
dc.titleDynamics and collisional evolution of closely packed planetary systemsen_US
dc.description.versionPublished articleen_US
dc.contributor.avlauthorLombardi, James C., Jr. (Jamie)

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