Infrared observations of white dwarfs and the implications for the accretion of dusty planetary material

Abstract

Infrared excesses around metal polluted white dwarfs have been associated with the accretion of dusty, planetary material. This work analyses the available infrared data for an unbiased sample of white dwarfs and demonstrates that no more than 3.3% can have a wide, flat, opaque dust disc, extending to the Roche radius, with a temperature at the disc inner edge of $T_{in}=1,400$K, the standard model for the observed excesses. This is in stark contrast to the incidence of pollution of about 30%. We present four potential reasons for the absence of an infrared excess in polluted white dwarfs, depending on their stellar properties and inferred accretion rates: i) their dust discs are opaque, but narrow, thus evading detection if more than 85% of polluted white dwarfs have dust discs narrower than $\delta r<0.04r$, ii) their dust discs have been fully consumed, which only works for the oldest white dwarfs with sinking timescales longer than hundreds of years, iii) their dust is optically thin, which can supply low accretion rates of $<10^7$gs${}^{-1}$ if dominated by PR-drag, and higher accretion rates, if inwards transport of material is enhanced, for example due to the presence of gas, iv) their accretion is supplied by a pure gas disc, which could result from the sublimation of optically thin dust for T* > 20, 000K. Future observations sensitive to faint infrared excesses or the presence of gas, can test the scenarios presented here, thereby better constraining the nature of the material fuelling accretion in polluted white dwarfs.

arXiv commentMNRAS, accepted

References in corpus (43)

• A Tidally-Disrupted Asteroid Around the White Dwarf G29-38
• A disintegrating minor planet transiting a white dwarf
• Are There Unstable Planetary Systems Around White Dwarfs?
• The frequency of planetary debris around young white dwarfs
• SDSS DR7 White Dwarf Catalog
• A gaseous metal disk around a white dwarf
• Ancient planetary systems are orbiting a large fraction of white dwarf stars
• Infrared Signatures of Disrupted Minor Planets at White Dwarfs
• Accretion and diffusion in white dwarfs. New diffusion timescales and applications to GD362 and G29-38
• Pollution of single white dwarfs by accretion of many small asteroids
• The Dust cloud around the White Dwarf G 29-38
• Externally-polluted white dwarfs with dust disks
• Global Models of Runaway Accretion in White Dwarf Debris Disks
• Constraints on the Lifetimes of Disks Resulting from Tidally Destroyed Rocky Planetary Bodies
• Six White Dwarfs with Circumstellar Silicates
• The frequency and infrared brightness of circumstellar discs at white dwarfs
• Runaway accretion of metals from compact debris disks onto white dwarfs
• Metal accretion onto white dwarfs caused by Poynting-Robertson drag on their debris disks
• The WIRED Survey II: Infrared Excesses in the SDSS DR7 White Dwarf Catalog
• Echoes of a decaying planetary system: the gaseous and dusty disks surrounding three white dwarfs
• SDSSJ104341.53+085558.2: A second white dwarf with a gaseous debris disc
• Strengthening the Case for Asteroidal Accrection: Evidence for Subtle and Diverse Disks at White Dwarfs
• Stochastic accretion of planetesimals onto white dwarfs: constraints on the mass distribution of accreted material from atmospheric pollution
• SDSSJ084539.17+225728.0: the first DBZ white dwarf with a metal-rich gaseous debris disc
• Spitzer IRAC Observations of White Dwarfs. I. Warm Dust at Metal-Rich Degenerates
• Infrared Emission from the Dusty Disk Orbiting GD 362, An Externally-Polluted White Dwarf
• High-speed photometry of the disintegrating planetesimals at WD1145+017: evidence for rapid dynamical evolution
• The Dust cloud around the White Dwarf G 29-38. 2. Spectrum from 5-40 microns and mid-infrared variability
• The bright end of the exo-Zodi luminosity function: Disk evolution and implications for exo-Earth detectability
• The Frequency of Debris Disks at White Dwarfs
• A Spitzer White Dwarf Infrared Survey
• Spitzer Observations of White Dwarfs: the Missing Planetary Debris Around DZ Stars
• A Dusty Component to the Gaseous Debris Disk around the White Dwarf SDSS J1228+1040
• The Drop during Less than 300 days of a Dusty White Dwarf's Infrared Luminosity
• The WIRED Survey I: A Bright IR Excess Due to Dust Around the Heavily Polluted White Dwarf GALEX J193156.8+011745
• A Spitzer Space Telescope Study of the Debris Disks around four SDSS White Dwarfs
• The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf Catalog
• Global modeling of radiatively driven accretion of metals from compact debris disks onto the white dwarfs
• Near-infrared emission from sublimating dust in collisionally active debris disks
• Dusty WDs in the $WISE$ All Sky Survey $\cap$ SDSS
• A Second Look at the Metal Line Variability of G29-38
• Keck Speckle Imaging of the White Dwarf G29-38: No Brown Dwarf Companion Detected
• Near-Infrared Imaging of White Dwarfs with Candidate Debris Disks

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• The dust never settles: collisional production of gas and dust in evolved planetary systems
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• 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
• Can tidal evolution lead to close-in planetary bodies around white dwarfs II: volcanism and transits
• White Dwarf Variability with gPhoton: Pulsators
• Binary asteroid scattering around white dwarfs
• White dwarf systems: exoplanets and debris disks
• PHL 5038AB: Is the brown dwarf causing pollution of its white dwarf host star?
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