Rapid destruction of planetary debris around white dwarfs through aeolian erosion

Abstract

The discovery of numerous debris disks around white dwarfs (WDs), gave rise to extensive study of such disks and their role in polluting WDs, but the formation and evolution of these disks is not yet well understood. Here we study the role of aeolian (wind) erosion in the evolution of solids in WD debris disks. Aeolian erosion is a destructive process that plays a key role in shaping the properties and size-distribution of planetesimals, boulders and pebbles in gaseous protoplanetary disks. Our analysis of aeolian erosion in WD debris disks shows it can also play an important role in these environments. We study the effects of aeolian erosion under different conditions of the disk, and its erosive effect on planetesimals and boulders of different sizes. We find that solid bodies smaller than $\sim 5 \, \rm {km}$ will be eroded within the short disk lifetime. We compare the role of aeolian erosion in respect to other destructive processes such as collisional fragmentation and thermal ablation. We find that aeolian erosion is the dominant destructive process for objects with radius $\lesssim 10^3 \, \rm {cm}$ and at distances ≲ 0.6 R⊙ from the WD. Thereby, aeolian erosion constitutes the main destructive pathway linking fragmentational collisions operating on large objects with sublimation of the smallest objects and Poynting-Robertson drag, which leads to the accretion of the smallest particles on to the photosphere of WDs, and the production of polluted WDs.

Collisions in a gas-rich white dwarf planetary debris disc

“…Numerous mechanisms have been proposed to perturb material onto nearly star-crossing orbits, of which only wide stellar companions have been shown to be unimportant (Debes & Sigurdsson 2002;Bonsor et al 2011;Bonsor & Veras 2015;Petrovich & Muñoz 2017;Mustill et al 2018;Wilson et al 2019;Smallwood et al 2021). The details of subsequent disc formation are largely unconstrained, although theoretical efforts have produced plausible models (Veras et al 2014(Veras et al , 2015Malamud & Perets 2020a,b), where interactions between solids and gas appear to play a key role (Grishin & Veras 2019;Rozner et al 2021;Malamud et al 2021). Disc lifetimes are uncertain, with model predictions in the range 10 1 -10 6 yr (Rafikov 2011b;Wyatt et al 2014), and observational estimates in the range 10 4 -10 6 yr (Girven et al 2012;Cunningham et al 2021).…”

White dwarf planetary debris dependence on physical structure distributions within asteroid belts

“…Bodies which move within a gas disc are subject to a gas drag dependent on the relative velocity of the object and the gas. This gas drag can cause outer layers of the body to be lost analagous to aeolian erosive winds (Rozner et al 2021).…”

The entry geometry and velocity of planetary debris into the Roche sphere of a white dwarf

“…These geometric details are crucial. They determine the type of debris structure formed (Malamud & Perets 2020a), the subsequent evolution of the rings and discs (Bochkarev & Rafikov 2011;Rafikov 2011a,b;Rafikov & Garmilla 2012;Kenyon & Bromley 2017a,b;Miranda & Rafikov 2018;Veras & Heng 2020;Malamud et al 2021;Rozner et al 2021;Trevascus et al 2021) and, ultimately, the accretion rates onto the photosphere. These rates are then used to reconstruct the chemical composition of the destroyed progenitor (e.g.…”