Photo-evaporation of proto-planetary gas discs due to flybys of external single stars in different orbits

TL;DR

This study investigates how flybys of external stars in different orbits affect the photo-evaporation and survival of proto-planetary gas discs, impacting planet formation in star clusters.

Contribution

It provides a criterion for gap-opening due to photo-evaporation after stellar flybys and analyzes how orbit parameters influence disc mass loss and lifetime.

Findings

Gap-opening occurs in late-stage gas discs due to photo-evaporation.

Maximum mass loss occurs at moderate peri-center distances, weakly dependent on orbit eccentricity and inclination.

Discs in open clusters typically survive 1-10 Myr, while in globular clusters they disperse quickly.

Abstract

During the evolution of proto-planetary disc, photo-evaporations of both central and external stars play important roles. Considering the complicated radiation surroundings in the clusters, where the star formed, the proto-planetary discs survive in different lifetimes due to flyby events. In this paper, we mainly focus on the disc around a T Tauri star, which encounters with another main-sequence star with different temperatures in hyperbolic orbits with different peri-center distances, eccentricities and inclinations. We find the criterion for gap-opening due to photo-evaporation of central star after the flyby event. A gap is opened in the late stage of gas disc, and induce that the gap only influence the planet formation and migration limitedly. If the flyby orbit has a moderate value of peri-center distance, which weakly depends on the eccentricity and inclination, the external photo-evaporation lead to a maximum mass loss during the flyby event. Flyby stars in orbits with smaller eccentricities or larger inclinations induce larger mass loss. Adopting a simple multiple flyby models, we conclude that in open clusters, gas discs usually survive in typical lifetimes between 1 and 10 Myr, except there are many massive stars in dense open clusters. In globular clusters, discs disperse very quickly and hardly produce the gas giant planets. The fast-depleted discs are probably responsible for the null detection of giant planets in globular clusters.