Effects of inclined star-disk encounter on protoplanetary disk size

TL;DR

This study uses numerical simulations to analyze how inclined star-disk encounters, including retrograde and prograde cases, affect protoplanetary disk sizes, providing insights relevant for observations and planetary system formation.

Contribution

It investigates the effects of inclined, retrograde star-disk encounters on disk size, a less explored scenario, with a comprehensive analysis including orbital parameters of disk particles.

Findings

Inclined and retrograde encounters significantly reduce disk size, especially at close periastron distances.

Prograde encounters show a nearly linear relationship between disk size and orbital inclination.

Disk particle orbital parameters are affected, influencing planetary system evolution.

Abstract

Most, if not all, young stars are initially surrounded by protoplanetary disks. Owing to the preferential formation of stars in stellar clusters, the protoplanetary disks around these stars may potentially be affected by the cluster environment. Various works have investigated the influence of stellar fly-bys on disks, although many of them consider only the effects due to parabolic, coplanar encounters often for equal-mass stars, which is only a very special case. We perform numerical simulations to study the fate of protoplanetary disks after the impact of parabolic star-disk encounter for the less investigated case of inclined up to coplanar, retrograde encounters, which is a much more common case. Here, we concentrate on the disk size after such encounters because this limits the size of the potentially forming planetary systems. In addition, with the possibilities that ALMA offers, now a direct comparison to observations is possible. Covering a wide range of periastron distances and mass ratios between the mass of the perturber and central star, we find that despite the prograde, coplanar encounters having the strongest effect on the disk size, inclined and even the least destructive retrograde encounters mostly also have a considerable effect, especially for close periastron passages. Interestingly, we find a nearly linear dependence of the disk size on the orbital inclination for the prograde encounters, but not for the retrograde case. We also determine the final orbital parameters of the particles in the disk such as eccentricities, inclinations, and semi-major axes. Using this information the presented study can be used to describe the fate of disks and also that of planetary systems after inclined encounters.