Disk dispersal freezes overstable resonant librations
Year: 2026
Type: article
Abstract: Context. Convergent migration in a gaseous protoplanetary disk can capture a planet pair into mean-motion resonance. Eccentricity damping can subsequently make the resonant libration overstable and drive the pair out of resonance. Most studies of this process, however, assumed a static disk. Aims. We examine how the decay of disk torques during dispersal changes this outcome and whether it can freeze an overstable libration before the pair escapes. Methods. We describe disk dispersal by allowing the migration and eccentricity-damping timescales to increase exponentially on a local timescale τ d . Integration of the time-dependent growth rate predicts τ d, crit ∝ τ e , 0 . We tested this scaling with direct N -body integrations and related τ d to the time taken by a photoevaporative cavity edge to cross the local torque-producing region. Results. The simulations recovered a linear boundary, τ d, crit ≃ Sτ e , 0 , with S ≃ 3 over the explored parameter range. In a fiducial minimum-mass solar nebula, faster propagation of the cavity edge shortened the local dispersal time. The ratio τ d / τ d, crit also decreased with orbital radius, which means that both effects favour resonant survival. Conclusions. When local disk dispersal is sufficiently rapid, the libration amplitude can freeze and the planet pair can remain in resonance instead of escaping through overstability. Late disk evolution can therefore alter the outcome of resonant overstability.
Source: Astronomy and Astrophysics
Authors: Linghong Lin, Beibei Liu
Institution: Zhejiang University
Language: English
Topic: Astro and Planetary Science
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Awards: G166518955, G351786161
OpenAlex ID: W7211905395