Photoevaporation of protoplanetary gas discs due to flybys of external single stars in different orbits

During the evolution of protoplanetary disc, photoevaporations of both central and external stars play important roles. Considering the complicated radiation surroundings in the clusters, where the star formed, the protoplanetary 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 pericentre distances, eccentricities, and inclinations. We find the criterion for gap opening due to photoevaporation of central star after the flyby event. A gap is opened in the late stage of gas disc, and induces that the gap only influence the planet formation and migration limitedly. If the flyby orbit has a moderate value of pericentre distance, which weakly depends on the eccentricity and inclination, the external photoevaporation 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.