Collisions in a gas-rich white dwarf planetary debris disc

TL;DR

This paper investigates the collisional processes in a gas-rich debris disc around a white dwarf, using observations and modeling to understand dust and gas production from ongoing collisions.

Contribution

It provides observational evidence and a simple model demonstrating that ongoing collisions drive dust and gas production in white dwarf debris discs.

Findings

Detection of stochastic brightening events indicating dust liberation.

Observation of decreasing infrared flux suggesting collisional evolution.

Presence of circumstellar gas supporting collisional gas production.

Abstract

WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3-5 micron flux since 2018. Follow-up Spitzer photometry reveals that emission from the disc had begun to decrease by late 2019. Stochastic brightening events superimposed on the decline in brightness suggest the liberation of dust during collisional evolution of the circumstellar solids. A simple model is used to show that the observations are indeed consistent with ongoing collisions. Rare emission lines from circumstellar gas have been detected at this system, supporting the emerging picture of white dwarf debris discs as sites of collisional gas and dust production.