Collisions in a gas-rich white dwarf planetary debris disc

Swan, Andrew; Kenyon, Scott J.; Farihi, Jay; Dennihy, Erik; Gänsicke, Boris T.; Hermes, J. J.; Melis, Carl; von Hippel, Ted

doi:10.48550/arxiv.2106.09025

Cited by 2 publications

(2 citation statements)

References 78 publications

(113 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These collisions take place while the fragments still travel along the highly eccentric orbits (e > 0.999) on which they are released. This notion is fundamentally different from previous models that calculated collisions between fragments that were already supposed to have circularised (Kenyon & Bromley 2017a,b;Swan et al 2021). In Sect.…”

Section: Introductioncontrasting

confidence: 63%

A road-map to white dwarf pollution: Tidal disruption, eccentric grind-down, and dust accretion

Brouwers,

Bonsor,

Malamud

2021

Preprint

View full text Add to dashboard Cite

A significant fraction of white dwarfs show metal lines indicative of pollution with planetary material but the accretion process remains poorly understood. The main aim of this paper is to produce a road-map illustrating several potential routes for white dwarf pollution and to link these paths to observational outcomes. Our proposed main road begins with the tidal disruption of a scattered asteroid and the formation of a highly eccentric tidal disc with a wide range of fragment sizes. Accretion of these fragments by Poynting-Robertson (PR) drag alone is too slow to explain the observed rates. Instead, in the second stage, several processes including differential apsidal precession cause high-velocity collisions between the eccentric fragments. Large asteroids produce more fragments when they disrupt, causing rapid grinddown and generating short and intense bursts of dust production, whereas smaller asteroids grind down over longer periods of time. In the final stage, the collisionally produced dust circularises and accretes onto the white dwarf via drag forces. We show that optically thin dust accretion by PR drag produces large infrared (IR) excesses when the accretion rate exceeds 10 7 g/s. We hypothesise that around white dwarfs accreting at a high rate, but with no detected infrared excess, dust circularisation requires enhanced drag -for instance due to the presence of gas near the disc's pericentre.

show abstract

Section: Introductioncontrasting

confidence: 63%

A road-map to white dwarf pollution: Tidal disruption, eccentric grind-down, and dust accretion

Brouwers,

Bonsor,

Malamud

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…In this scenario, where sublimative erosion outpaces alternative accretion processes such as scattering, collisional grind-down and drag forces (e.g. Veras et al 2015;Swan et al 2021;Li et al 2021;Malamud et al 2021;Brouwers et al 2022b), the ice and rock in a pollutant will largely accrete separately, and the photospheric abundances of white dwarfs do not necessarily reflect the bulk composition of their pollutants. We focus on defining observational predictions that result from this form of asynchronous accretion, and collate a white dwarf sample from the literature to test these predictions.…”

Section: Introductionmentioning

confidence: 99%

Asynchronous accretion can mimic diverse white dwarf pollutants II: water content

Brouwers¹,

Buchan²,

Bonsor³

et al. 2022

Preprint

View full text Add to dashboard Cite

Volatiles, notably water, are key to the habitability of rocky planets. The presence of water in planetary material can be inferred from the atmospheric oxygen abundances of polluted white dwarfs, but this interpretation is often complex. We study the accretion process, and find that ices may sublimate and accrete before more refractory minerals reach the star. As a result, a white dwarf's relative photospheric abundances may vary with time during a single accretion event, and do not necessarily reflect the bulk composition of a pollutant. We offer two testable predictions for this hypothesis: 1. cooler stars will more often be inferred to have accreted wet pollutants, and 2. there will be rare occurrences of accretion events with inferred volatile levels far exceeding those of pristine comets. To observationally test these predictions, we statistically constrain the water content of white dwarf pollutants. We find that in the current sample, only three stars show statistically significant evidence of water at the 2σ level, due to large typical uncertainties in atmospheric abundances and accretion states. In the future, an expanded sample of polluted white dwarfs with hydrogen-dominated atmospheres will allow for the corroboration of our theoretical predictions. Our work also shows the importance of interpreting pollutant compositions statistically, and emphasizes the requirement to reduce uncertainties on measured abundances to allow for statistically significant constraints on their water content.

show abstract

Collisions in a gas-rich white dwarf planetary debris disc

Cited by 2 publications

References 78 publications

A road-map to white dwarf pollution: Tidal disruption, eccentric grind-down, and dust accretion

A road-map to white dwarf pollution: Tidal disruption, eccentric grind-down, and dust accretion

Asynchronous accretion can mimic diverse white dwarf pollutants II: water content

Contact Info

Product

Resources

About