Apsidal alignment and anti-alignment of planets in mean-motion resonance: disc-driven migration and eccentricity driving

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