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dc.contributor.authorHwang, Jason A.
dc.contributor.authorChatterjee, Sourav
dc.contributor.authorLombardi, James C. Jr
dc.contributor.authorSteffen, Jason H.
dc.contributor.authorRasio, Frederic A.
dc.date.accessioned2017-10-13T14:33:37Z
dc.date.available2017-10-13T14:33:37Z
dc.date.issued2017
dc.identifier.urihttp://hdl.handle.net/10456/45221
dc.identifier.urihttps://doi.org/10.3847/1538-4357/aa9d42
dc.description.abstractMany studies of high-multiplicity, tightly-packed planetary systems, similar to those observed in the Kepler sample, suggest that dynamical instabilities are common and affect both the orbits and planet structures. The compact orbits and typically low densities make physical collisions likely outcomes of these instabilities. Since the structure of many of these planets is such that the mass is dominated by a rocky core, but the volume is dominated by a tenuous gas envelope, the sticky-sphere prescription, used in dynamical integrators, may be a poor approximation for these collisions. We perform five sets of collision calculations, including detailed hydrodynamics, sampling mass ratios and core mass-fractions typical in Kepler Multis. In our primary set of calculations, we use Kepler-36 as a nominal remnant system, as the two planets have a small dynamical separation and an extreme density ratio, which may be indicative of a previous planet-planet collision, where the more massive planet was able to retain a majority of the disrupted gas, while the smaller planet lost much of its gas envelope. We use an N-body code, Mercury 6.2, to dynamically integrate initially unstable systems and study the resultant planet-planet collisions in detail. We use these collisions, focusing on grazing collisions, in combination with realistic planet models created using the gas profiles from Modules for Experiments in Stellar Astrophysics (MESA) and equations of state from Seager et al. (2007), to perform detailed hydrodynamic calculations, finding several distinct outcomes including scatterings, mergers, and even a potential planet-planet binary. We dynamically integrate the remnant systems, examine the stability, and estimate the final densities. We find the remnant densities are very sensitive to the core masses and collisions result in generally more stable systems. Finally, we provide prescriptions for predicting the outcomes and modeling the changes in mass and orbits following planet-planet collisions for general use in dynamical integrators, improving on the sticky-sphere approximation.en_US
dc.language.isoen_USen_US
dc.publisherAmerican Astronomical Societyen_US
dc.relation.ispartofAmerican Astronomical Societyen_US
dc.subjectequation of stateen_US
dc.subjecthydrodynamicsen_US
dc.subjectmethods: numericalen_US
dc.subjectplanets and satellites: dynamical evolution and stability, gaseous planetsen_US
dc.subjectstars: individual: (Kepler-36)en_US
dc.titleHydrodynamics of Collisions Between Sub-Neptunesen_US
dc.contributor.departmentPhysicsen_US
dc.contributor.avlauthorLombardi, James C. Jr


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