# Flybys in protoplanetary discs: I. Gas and dust dynamics

**Authors:** Nicolás Cuello, Giovanni Dipierro, Daniel Mentiplay, Daniel J. Price, Christophe Pinte, Jorge Cuadra, Guillaume Laibe, François Ménard, Pedro P. Poblete, Matías Montesinos  
**arXiv:** [1812.00961](https://arxiv.org/abs/1812.00961)  
**Date:** 2018-12-03  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/1812.00961v1/

## Key points

- The study is titled "Flybys in protoplanetary discs: I. Gas and Dust Dynamics"
- The study uses 3D smoothed particle hydrodynamics simulations to model protoplanetary discs undergoing a flyby by a stellar perturber on a parabolic orbit lying in a plane inclined relative to the disc mid-plane
- The team models the disc as a mixture of gas and dust, with grains ranging from 1 μm to 10 cm in size
- The researchers find that flybys induce evolving spiral structure in both gas and dust which can persist for thousands of years after periastron passage
- Due to drag-induced effects on dust grains, gas and dust structures induced by the flyby differ significantly
- Variations in the accretion rate by up to an order of magnitude occur over a time-scale of around 10 years or less; these variations can lead to FU Orionis-like outbursts
- Remnant discs are truncated and warped with the dust disc being more compact than the gas disc due to both disc truncation and accelerated radial drift of grains induced by the flyby
- These findings suggest that such events could play an important role in shaping planetary systems' evolution through their impact on planet formation processes

## Summary

In their study, "Flybys in protoplanetary discs: I. Gas and Dust Dynamics," Nicolás Cuello and colleagues present 3D smoothed particle hydrodynamics simulations of protoplanetary discs undergoing a flyby by a stellar perturber on a parabolic orbit lying in a plane inclined relative to the disc mid-plane. The team models the disc as a mixture of gas and dust, with grains ranging from 1 {\mu}m to 10 cm in size, exploring different orbital inclinations, periastron distances, and mass ratios to investigate the disc's dynamical response during and after the flyby. The researchers find that flybys induce evolving spiral structure in both gas and dust which can persist for thousands of years after periastron passage. However, due to drag-induced effects on dust grains, gas and dust structures induced by the flyby differ significantly. Variations in the accretion rate by up to an order of magnitude occur over a time-scale of around 10 years or less; these variations can lead to FU Orionis-like outbursts. Moreover, Cuello et al. observe that the remnant discs are truncated and warped with the dust disc being more compact than the gas disc due to both disc truncation and accelerated radial drift of grains induced by the flyby. These findings suggest that such events could play an important role in shaping planetary systems' evolution through their impact on planet formation processes. Overall, this study provides new insights into how stellar perturbations can affect protoplanetary discs' dynamics and structure over long timescales.