# Embedding planetesimals into white dwarf discs from large distances

## TL;DR

This paper develops an analytical model to estimate how white dwarf debris discs can capture exo-planetesimals from various sources, revealing that capture is size-dependent and more likely in extended gaseous discs, impacting disc evolution.

## Contribution

It introduces a new formalism to quantify the capture rate of exo-planetesimals by white dwarf discs from different origins, considering size and disc extent.

## Key findings

- Capture of interstellar planetesimals is negligible.
- Capture of exo-Kuiper and exo-Oort bodies is viable and size-dependent.
- Disc size and extent significantly influence capture probability.

## Abstract

The discovery of the intact minor planet embedded in the debris disc orbiting SDSS J1228+1040 raises questions about the dynamical history of the system. Further, the recent passage of the potentially interstellar object 1I/'Oumuamua within the solar system has re-ignited interest in minor body flux through exoplanetary systems. Here, we utilize the new analytical formalism from Grishin, Perets and Avni (2019) to estimate the rate at which the gaseous components of typical white dwarf discs trap an exo-planetesimal. We compare the types of captured orbits which arise from planetesimals originating from the interstellar medium, exo-Kuiper belts and exo-Oort clouds. We find that the rate of interstellar medium injection is negligible, whereas capture of both exo-Kuiper and exo-Oort cloud planetesimals is viable, but strongly size-dependent. For a gaseous disc which extends much beyond its Roche limit, capture is more probable than disruption at the Roche limit. We find that the capture probability linearly increases with the radial extent of the disc. Even in systems without minor planets, capture of smaller bodies will change the disc size distribution and potentially its temporal variability. Our formalism is general enough to be applied to future discoveries of embedded planetesimals in white dwarf debris discs.