F.S.I.: Flyby Scene Investigation

TL;DR

This paper introduces a methodology to interpret observational signatures of protoplanetary discs affected by flybys, helping to infer encounter parameters and understand disc evolution and disturbances.

Contribution

It presents a novel approach to analyze and interpret the dynamical and kinematical signatures of flybys in protoplanetary discs across multiple wavelengths.

Findings

Flybys cause long-lasting disc disturbances like spirals, warps, and cavities.

Dust and gas respond differently to flybys due to gas-drag effects.

Flybys can trigger star accretion outbursts similar to FU Orionis events.

Abstract

We present a methodology to interpret observations of protoplanetary discs where a flyby, also called a tidal encounter, is suspected. In case of a flyby, protoplanetary discs can be significantly disturbed. The resulting dynamical and kinematical signatures can last for several thousands of years after the flyby and hence deeply affect the evolution of the disc. These effects are stronger for closer encounters and more massive perturbers. For the very same flyby parameters, varying the inclination of the perturber's orbit produces a broad range of disc structures: spirals, bridges, warps and cavities. We study this kind of features both in the gas and in the dust for grains ranging from 1 {\mu}m to 10 cm in size. Interestingly, the dust exhibits a different dynamical behaviour compared to the gas because of gas-drag effects. Finally, flybys can also trigger high accretion events in the disc-hosting star, readily similar to FU Orionis-type outbursts. All this information can be used to infer the flyby parameters from an incomplete set of observations at different wavelengths. Therefore, the main scope of our flyby scene investigation (FSI) methodology is to help to interpret recent "puzzling" disc observations.