Dynamical evolution of an eccentric planet and a less massive debris disc

Abstract

We investigate the interaction between an eccentric planet and a less massive external debris disc. This scenario could occur after planet-planet scattering or merging events. We characterise the evolution over a wide range of initial conditions, using a suite of n-body integrations combined with theory. Planets near the disc mid-plane remove the inner debris region, and surviving particles form an eccentric disc apsidally aligned with the planet. The inner disc edge is elliptical and lies just beyond the planet's orbit. Moderately inclined planets (i plt 20• for e plt = 0.8) may instead sculpt debris into a bell-shaped structure enveloping the planet's orbit. Finally some highly inclined planets (i plt ∼ 90• ) can maintain a disc orthogonal to the planet's plane. In all cases disc particles undergo rapid evolution, whilst the overall structures evolve more slowly. The shapes of these structures and their density profiles are characterised. The width of the chaotic zone around the planet's orbit is derived in the coplanar case using eccentric Hill radius arguments. This zone is cleared within approximately ten secular or diffusion times (whichever is longer), and debris assumes its final shape within a few secular times. We quantify the planet's migration and show it will almost always be small in this mass regime. Our results may be used to characterise unseen eccentric planets using observed debris features.

Apocenter Glow in Eccentric Debris Disks: Implications for Fomalhaut and Ε Eridani

“…Though modeling done by Wyatt et al (1999) predicted a brightness enhancement at pericenter for HR 4796 at 18.2 μm, their disk model showed a 2% density enhancement at apocenter. Analogous apocentric density enhancements occur in more recent dynamical models of eccentric planets interacting with disks (see, for example, Nesvold et al 2013;Pearce & Wyatt 2014). Indeed, submillimeter observations of the very well-observed eccentric Fomalhaut disk consistently suggest apocentric brightness enhancements.…”

Resolving the planetesimal belt of HR 8799 with ALMA

“…Such a planet would need to be beyond the chaotic zone of planet b to have any possibility of being stable. Using the equations of Pearce & Wyatt (2014), a planet at the edge of planet b's chaotic zone (110 AU) on a circular orbit would need to be ∼1.25 MJ to create an inner edge at 145 AU. If it was further out or on an eccentric orbit, the required mass of the extra planet would be lower.…”

A Complete ALMA Map of the Fomalhaut Debris Disk

“…However, it is likely that this slight asymmetry between the NE and SW sides of the disk presents further evidence for apocenter glow. The expected overdensity of particles at apocenter forms an arc, which would cover much of the eastern side of the disk given the observed disk geometry (Pan et al 2016;Pearce & Wyatt 2014).…”