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

Abstract

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 grind-down 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.

Published in MNRAS

References in corpus (42)

• The frequency of planetary debris around young white dwarfs
• A gaseous metal disk around a white dwarf
• Transience of hot dust around sun-like stars
• The Chemical Composition of an Extrasolar Minor Planet
• Foretellings of Ragnarök: World-engulfing Asymptotic Giants and the Inheritance of White Dwarfs
• Hot Jupiters and Cool Stars
• Formation of planetary debris discs around white dwarfs I: Tidal disruption of an extremely eccentric asteroid
• A planetesimal orbiting within the debris disc around a white dwarf star
• The frequency and infrared brightness of circumstellar discs at white dwarfs
• The Chemical Composition of an Extrasolar Kuiper-Belt-Object
• SDSSJ104341.53+085558.2: A second white dwarf with a gaseous debris disc
• Infrared Emission from the Dusty Disk Orbiting GD 362, An Externally-Polluted White Dwarf
• The unbiased frequency of planetary signatures around single and binary white dwarfs using $Spitzer$ and $Hubble$
• Cool DZ white dwarfs I: Identification and spectral analysis
• Scars of Intense Accretion Episodes at Metal-Rich White Dwarfs
• Numerical Simulations of Collisional Cascades at the Roche Limits of White Dwarf Stars
• Lense-Thirring frame dragging induced by a fast-rotating white dwarf in a binary pulsar system
• Tidal disruption of planetary bodies by white dwarfs I: A hybrid SPH-analytical approach
• The orbital evolution of asteroids, pebbles and planets from giant branch stellar radiation and winds
• The frequency of gaseous debris discs around white dwarfs
• Convective Overshoot and Macroscopic Diffusion in Pure-Hydrogen Atmosphere White Dwarfs
• Are exoplanetesimals differentiated?
• Dusty tails of evaporating exoplanets. I. Constraints on the dust composition
• Tidal disruption of planetary bodies by white dwarfs II: Debris disc structure and ejected interstellar asteroids
• Most white dwarfs with detectable dust discs show infrared variability
• Horizontal spreading of planetary debris accreted by white dwarfs
• The dust never settles: collisional production of gas and dust in evolved planetary systems
• Bayesian constraints on the origin and geology of exo-planetary material using a population of externally polluted white dwarfs
• Circularization of tidal debris around white dwarfs: implications for gas production and dust variability
• Speeding past planets? Asteroids radiatively propelled by giant branch Yarkovsky effects
• Linking long-term planetary $N$-body simulations with periodic orbits: application to white dwarf pollution
• Post-main-sequence debris from rotation-induced YORP break-up of small bodies II: multiple fissions, internal strengths and binary production
• Do instabilities in high-multiplicity systems explain the existence of close-in white dwarf planets?
• Understanding the origin of white dwarf atmospheric pollution by dynamical simulations based on detected three-planet systems
• Collisions in a gas-rich white dwarf planetary debris disc
• Accretion of tidally disrupted asteroids onto white dwarfs: direct accretion versus disk processing
• ALMA and Herschel Observations of the Prototype Dusty and Polluted White Dwarf G29-38
• A Characterization of the Circumstellar Gas around WD 1124-293 using Cloudy
• The entry geometry and velocity of planetary debris into the Roche sphere of a white dwarf
• White dwarf planetary debris dependence on physical structure distributions within asteroid belts
• Emission from elliptical streams of dusty debris around white dwarfs
• Explorations of Dusty Debris Disk Geometry

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• Asynchronous accretion can mimic diverse white dwarf pollutants II: water content
• The smallest planetary drivers of white dwarf pollution
• Discovery of magnetically guided metal accretion onto a polluted white dwarf
• Dynamics of the clumps partially disrupted from a planet around a neutron star
• Magnetic interactions in orbital dynamics
• Can tidal evolution lead to close-in planetary bodies around white dwarfs I: Orbital period distribution
• High-resolution resonant portraits of a single-planet white dwarf system
• White dwarf systems: exoplanets and debris disks
• Characterizing planetary material accreted by cool helium atmosphere white dwarfs using an exponentially decaying disc model
• Planetesimals drifting through dusty and gaseous white dwarf debris discs: Types I, II and III-like migration
• Partial disruption of a planet around a white dwarf: the effect of perturbation from the remnant planet on the accretion
• PHL 5038AB: Is the brown dwarf causing pollution of its white dwarf host star?
• Planets or asteroids? A geochemical method to constrain the masses of White Dwarf pollutants
• Detecting water ice and vapor disks originating from icy planetary bodies around white dwarfs with future PRIMA observations