Are exoplanetesimals differentiated?

Abstract

Metals observed in the atmospheres of white dwarfs suggest that many have recently accreted planetary bodies. In some cases, the compositions observed suggest the accretion of material dominantly from the core (or the mantle) of a differentiated planetary body. Collisions between differentiated exoplanetesimals produce such fragments. In this work, we take advantage of the large numbers of white dwarfs where at least one siderophile (core-loving) and one lithophile (rock-loving) species have been detected to assess how commonly exoplanetesimals differentiate. We utilise N-body simulations that track the fate of core and mantle material during the collisional evolution of planetary systems to show that most remnants of differentiated planetesimals retain core fractions similar to their parents, whilst some are extremely core-rich or mantle-rich. Comparison with the white dwarf data for calcium and iron indicates that the data are consistent with a model in which $66_{-6}^{+4}\%$ have accreted the remnants of differentiated planetesimals, whilst $31_{-5}^{+5}\%$ have Ca/Fe abundances altered by the effects of heating (although the former can be as high as $100\%$, if heating is ignored). These conclusions assume pollution by a single body and that collisional evolution retains similar features across diverse planetary systems. These results imply that both collisions and differentiation are key processes in exoplanetary systems. We highlight the need for a larger sample of polluted white dwarfs with precisely determined metal abundances to better understand the process of differentiation in exoplanetary systems.

18 pages, MNRAS, accepted

References in corpus (58)

• emcee: The MCMC Hammer
• Comprehensive analytic formulae for stellar evolution as a function of mass and metallicity
• A Tidally-Disrupted Asteroid Around the White Dwarf G29-38
• Are There Unstable Planetary Systems Around White Dwarfs?
• Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water
• The frequency of planetary debris around young white dwarfs
• Debris Disk Evolution Around A Stars
• Ancient planetary systems are orbiting a large fraction of white dwarf stars
• Spectral Properties of Cool Stars: Extended Abundance Analysis of 1617 Planet Search Stars
• Debris Disks: Structure, Composition, and Variability
• Accretion and diffusion in white dwarfs. New diffusion timescales and applications to GD362 and G29-38
• The Link Between Planetary Systems, Dusty White Dwarfs, and Metal Polluted White Dwarfs
• Circumstellar Debris and Pollution at White Dwarf Stars
• Steady-state evolution of debris disks around A stars
• Dynamical effects of stellar mass loss on a Kuiper-like belt
• Formation of planetary debris discs around white dwarfs I: Tidal disruption of an extremely eccentric asteroid
• Evidence for Water in the Rocky Debris of a Disrupted Extrasolar Minor Planet
• Simulations of two-planet systems through all phases of stellar evolution: implications for the instability boundary and white dwarf pollution
• Debris disc stirring by secular perturbations from giant planets
• Elemental Compositions of Two Extrasolar Rocky Planetesimals
• Minimum Radii of Super-Earths: Constraints from Giant Impacts
• Cool DZ white dwarfs II: Compositions and evolution of old remnant planetary systems
• An aluminum/calcium-rich, iron-poor, white dwarf star: evidence for an extrasolar planetary lithosphere?
• The Chemical Composition of an Extrasolar Kuiper-Belt-Object
• Long-term evolution of three-planet systems to the post-Main Sequence and beyond
• Detailed compositional analysis of the heavily polluted DBZ white dwarf SDSS J073842.56+183509.06: A window on planet formation?
• Collisional Stripping and Disruption of Super-Earths
• Likely detection of water-rich asteroid debris in a metal-polluted white dwarf
• Polluted White Dwarfs: Constraints on the Origin and Geology of Exoplanetary Material
• Two Beyond-Primitive Extrasolar Planetesimals
• Rocky Extrasolar Planetary Compositions Derived from Externally-Polluted White Dwarfs
• Cool DZ white dwarfs I: Identification and spectral analysis
• Compositional evolution during rocky protoplanet accretion
• Are debris disks self-stirred?
• Possible Signs of Water and Differentiation in a Rocky Exoplanetary Body
• A Collisional Origin to Earth's Non-chondritic Composition?
• Two Extrasolar Asteroids with Low Volatile-Element Mass Fractions
• Interpretation and diversity of exoplanetary material orbiting white dwarfs
• 26Al in the Early Solar System: Not so Unusual After All
• The Supernova Triggered Formation and Enrichment of Our Solar System
• Inheritance of solar short- and long-lived radionuclides from molecular clouds and the unexceptional nature of the solar system
• Convective Overshoot and Macroscopic Diffusion in Pure-Hydrogen Atmosphere White Dwarfs
• Simultaneous Triggered Collapse of the Presolar Dense Cloud Core and Injection of Short-Lived Radioisotopes by a Supernova Shock Wave
• Isotopic enrichment of forming planetary systems from supernova pollution
• Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
• Polluted White Dwarfs: Mixing Regions and Diffusion Timescales
• Collisional stripping of planetary crusts
• Solar Abundances of Rock Forming Elements, Extreme Oxygen and Hydrogen in a Young Polluted White Dwarf
• Who Pulled the Trigger: a Supernova or an AGB Star?
• Post main sequence evolution of icy minor planets: Implications for water retention and white dwarf pollution
• Increases to Inferred Rates of Planetesimal Accretion Due to Thermohaline Mixing in Metal Accreting White Dwarfs
• Numerically Predicted Indirect Signatures of Terrestrial Planet Formation
• Fingering convection induced by atomic diffusion in stars: 3D numerical computations and applications to stellar models
• Triggered Star Formation and Its Consequences
• Importance of fingering convection for accreting white dwarfs in the framework of full evolutionary calculations: the case of the hydrogen-rich white dwarfs GD133 and G29-38
• VLT/X-shooter observations and the chemical composition of cool white dwarfs
• Modelling the distributions of white dwarf atmospheric pollution: a low Mg abundance for accreted planetesimals?
• Extreme abundance ratios in the polluted atmosphere of the cool white dwarf NLTT19868

Cited by in corpus (48)

• Planetary Systems Around White Dwarfs
• The Atmospheres of Rocky Exoplanets I. Outgassing of Common Rock and the Stability of Liquid Water
• Alkali metals in white dwarf atmospheres as tracers of ancient planetary crusts
• The White Dwarf Opportunity: Robust Detections of Molecules in Earth-like Exoplanet Atmospheres with the James Webb Space Telescope
• Horizontal spreading of planetary debris accreted by white dwarfs
• Polluted White Dwarfs Reveal Exotic Mantle Rock Types on Exoplanets in our Solar Neighborhood
• Plausible constraints on the range of bulk terrestrial exoplanet compositions in the Solar neighbourhood
• A road-map to white dwarf pollution: Tidal disruption, eccentric grind-down, and dust accretion
• Lithium pollution of a white dwarf records the accretion of an extrasolar planetesimal
• Super-Earths and Earth-like Exoplanets
• The distribution of volatile elements during rocky planet formation
• The lifetimes of planetary debris discs around white dwarfs
• The spectral evolution of white dwarfs: where do we stand?
• Icy Exomoons Evidenced by Spallogenic Nuclides in Polluted White Dwarfs
• New chondritic bodies identified in eight oxygen-bearing white dwarfs
• Understanding the origin of white dwarf atmospheric pollution by dynamical simulations based on detected three-planet systems
• Magnesium abundances in cool metal-polluted white dwarfs
• High-eccentricity migration of planetesimals around polluted white dwarfs
• GD424 -- a helium-atmosphere white dwarf with a large amount of trace hydrogen in the process of digesting a rocky planetesimal
• The dynamical history of the evaporating or disrupted ice giant planet around white dwarf WD J0914+1914
• PEWDD: A database of white dwarfs enriched by exo-planetary material
• Asynchronous accretion can mimic diverse white dwarf pollutants I: core and mantle fragments
• Secular chaos in white-dwarf planetary systems: origins of metal pollution and short-period planetary companions
• Reduced late bombardment on rocky exoplanets around M-dwarfs
• On the role of resonances in polluting white dwarfs by asteroids
• Linking the formation and fate of exo-Kuiper belts within solar system analogues
• Necroplanetology: Simulating the Tidal Disruption of Differentiated Planetary Material Orbiting WD 1145+017
• Rapid Formation of Exoplanetesimals Revealed by White Dwarfs
• Prevalence of short-lived radioactive isotopes across exoplanetary systems inferred from polluted white dwarfs
• The Atmospheres of Rocky Exoplanets II. Influence of surface composition on the diversity of cloud condensates
• The white dwarf planet WD J0914+1914 b: barricading potential rocky pollutants?
• The sulphur species in hot rocky exoplanet atmospheres
• The grain size survival threshold in one-planet post-main-sequence exoplanetary systems
• Revisiting equilibrium condensation and rocky planet compositions: Introducing the ECCOplanets code
• Generating metal-polluting debris in white dwarf planetary systems from small-impact crater ejecta
• Asteroid belt survival through stellar evolution: dependence on the stellar mass
• Imaging of exocomets with infrared interferometry
• Short-lived radioisotope enrichment in star-forming regions from stellar winds and supernovae
• Rapid destruction of planetary debris around white dwarfs through aeolian erosion
• Post-main sequence thermal evolution of planetesimals
• Short-term stability of particles in the WD J0914+1914 white dwarf planetary system
• Reinterpreting the Polluted White Dwarf SDSS J122859.93+104032.9 in Light of Thermohaline Mixing Models: More Polluting Material from a Larger Orbiting Solid Body
• Planetesimals drifting through dusty and gaseous white dwarf debris discs: Types I, II and III-like migration
• White dwarf constraints on geological processes at the population level
• Metal-silicate mixing in planetesimal collisions
• Debris Disks
• Diversity of Exoplanets
• Planets or asteroids? A geochemical method to constrain the masses of White Dwarf pollutants