Apsidal Alignment and Anti-Alignment of Planets in Mean-Motion Resonance: Disk-Driven Migration and Eccentricity Driving

Abstract

Planets migrating in their natal discs can be captured into mean-motion resonance (MMR), in which the planets' periods are related by integer ratios. Recent observations indicate that planets in MMR can be either apsidally aligned or anti-aligned. How these different configurations arise is unclear. In this paper, we study the MMR capture process of migrating planets, focusing on the property of the apsidal angles of the captured planets. We show that the standard picture of MMR capture, in which the planets undergo convergent migration and experience eccentricity damping due to planet-disc interactions, always leads to apsidal anti-alignment of the captured planets. However, when the planets experience eccentricity driving from the disc, apsidally aligned configuration in MMR can be produced. In this configuration, both planets' resonance angles circulate, but a "mixed" resonance angle librates and traps the planets near the nominal resonance location. The MMR capture process in the presence of disc eccentricity driving is generally complex and irregular, and can lead to various outcomes, including apsidal alignment and anti-alignment, as well as the disruption of the resonance. We suggest that the two resonant planets in the K2-19 system, with their moderate eccentricities and aligned apsides, have experienced eccentricity driving from their natal disc in the past.

19 pages, 16 figures

References in corpus (14)

• Three-dimensional simulations of multiple protoplanets embedded in a protostellar disc
• Resonant Repulsion of Kepler Planet Pairs
• Planetesimal Interactions Can Explain the Mysterious Period Ratios of Small Near-Resonant Planets
• HD45364, a pair of planets in a 3:2 mean motion resonance
• Tidal dissipation and the formation of Kepler near-resonant planets
• Secular evolution of eccentricity in protoplanetary discs with gap-opening planets
• Sub-Neptune Formation: The View from Resonant Planets
• K2-19b and c are in a 3:2 Commensurability but out of Resonance: A Challenge to Planet Assembly by Convergent Migration
• Resonance in the K2-19 system is at odds with its high reported eccentricities
• Trapping of Low-Mass Planets Outside the Truncated Inner Edges of Protoplanetary Discs
• Modeling Radial Velocity Data of Resonant Planets to Infer Migration Histories
• Trapping (sub-)Neptunes similar to TOI-216b at the inner disk rim: Implications for the disk viscosity and the Neptunian desert
• Eccentricity driving of pebble accreting low-mass planets
• Exploiting periodic orbits as dynamical clues for Kepler and K2 systems

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• exoMMR: a New Python Package to Confirm and Characterize Mean Motion Resonances
• Accretion of aerodynamically large pebbles
• NIRPS tightens the mass estimate of GJ 3090 b and detects a planet near the stellar rotation period