New migration patterns in high planet-star mass ratio systems in disks with low viscosity

Migration of giant planets remains a complex topic. While significant progress has been made for high-viscosity disks, the migration of planets with large planet-star mass ratios in low-viscosity environments is still not fully understood. We study the migration of such planets in disks with α= 10^-4 and derive analytical prescriptions applicable across stellar masses, from Sun-like stars to M dwarfs. Using hydrodynamical simulations with FARGO3D, we explored planets with mass ratios 10^-3 0. 002. For planets undergoing outward migration, the migration speed depends on the unperturbed local gas density. In most cases, outward migration is sustained by a positive torque related to planetary eccentricities below e 0. 01 reach higher eccentricities (0. 2 < e < 0. 45), leading to stalled migration. Our findings suggest that outward migration is a viable mechanism for massive planets in low-viscosity disks, which has implications for the formation and distribution of super-Jupiter planets around Sun-like stars and planets more massive than Neptune around very low-mass stars. Given the challenges in detecting such planets, improving our theoretical understanding of their migration is essential for interpreting exoplanet demographics and guiding future observational efforts.