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Eccentricity evolution during planet-disc interaction

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Ragusa, E 
Teyssandier, J 
Clarke, CJ 


During the process of planet formation, the planet-disc interactions might excite (or damp) the orbital eccentricity of the planet. In this paper, we present two long (t ~ 3 × 10 5 orbits) numerical simulations: (a) one (with a relatively light disc, M d /M p = 0.2), where the eccentricity initially stalls before growing at later times and (b) one (with a more massive disc, M d /M p = 0.65) with fast growth and a late decrease of the eccentricity. We recover the well-known result that a more massive disc promotes a faster initial growth of the planet eccentricity. However, at late times the planet eccentricity decreases in the massive disc case, but increases in the light disc case. Both simulations show periodic eccentricity oscillations superimposed on a growing/decreasing trend and a rapid transition between fast and slow pericentre precession. The peculiar and contrasting evolution of the eccentricity of both planet and disc in the two simulations can be understood by invoking a simple toy model where the disc is treated as a second point-like gravitating body, subject to secular planet-planet interaction and eccentricity pumping/damping provided by the disc. We show how the counterintuitive result that the more massive simulation produces a lower planet eccentricity at late times can be understood in terms of the different ratios of the disc-to-planet angular momentum in the two simulations. In our interpretation, at late times the planet eccentricity can increase more in low-mass discs rather than in high-mass discs, contrary to previous claims in the literature.



planets and satellites: formation, planet–disc interactions, protoplanetary discs

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Monthly Notices of the Royal Astronomical Society

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Oxford University Press
European Research Council (341137)
Science and Technology Facilities Council (ST/L000636/1)
Science and Technology Facilities Council (ST/P000673/1)
Science and Technology Facilities Council (ST/M007065/1)
Science and Technology Facilities Council (ST/N000927/1)
This work has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. JT acknowledges support from STFC through grant ST/L000636/1. This work used the Wilkes GPU cluster at the University of Cambridge High Performance Computing Service (, provided by Dell Inc., NVIDIA and Mellanox, and part funded by STFC with industrial sponsorship from Rolls Royce and Mitsubishi Heavy Industries. We also thank the MIAPP for hosting us for the ‘Protoplanetary Disks and Planet Formation and Evolution’ topical workshop held in Munich during June 2017. All the figures were generated with the python-based package matplotlib (Hunter 2007).