White dwarf planetary systems Alexander Mustill Lund Observatory - - PowerPoint PPT Presentation

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White dwarf planetary systems Alexander Mustill Lund Observatory - - PowerPoint PPT Presentation

Jan 16, 2024 161 likes •545 views

White dwarf planetary systems Alexander Mustill Lund Observatory Collaborators: Amy Bonsor, Melvyn B. Davies, Jay Farihi, Boris Gnsicke, Ral Maldonado, Chris Manser, Dimitri Veras, Eva Villaver, Mark Wyatt, White dwarfs tell us what

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Alexander Mustill Lund Observatory

Collaborators: Amy Bonsor, Melvyn B. Davies, Jay Farihi, Boris Gänsicke, Raúl Maldonado, Chris Manser, Dimitri Veras, Eva Villaver, Mark Wyatt, …

White dwarf planetary systems

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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

White dwarfs tell us what extra-Solar planets and asteroids are made of

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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

White dwarfs tell us what extra-Solar planets and asteroids are made of

  • ~50% of WDs show metal lines in their spectra
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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

White dwarfs tell us what extra-Solar planets and asteroids are made of

  • ~50% of WDs show metal lines in their spectra
  • Metals should sink on short timescales: accretion is ongoing or recent
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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

White dwarfs tell us what extra-Solar planets and asteroids are made of

  • ~50% of WDs show metal lines in their spectra
  • Metals should sink on short timescales: accretion is ongoing or recent
  • Leading candidate: pulverised asteroids/planets scattered close to the WD
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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

White dwarfs tell us what extra-Solar planets and asteroids are made of

  • ~50% of WDs show metal lines in their spectra
  • Metals should sink on short timescales: accretion is ongoing or recent
  • Leading candidate: pulverised asteroids/planets scattered close to the WD
  • Composition gives us insight into planetary and asteroidal compositions

beyond the Solar System (review: Jura & Young 2014)

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White dwarf planetary systems: discs and close-in planetesimals

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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White dwarf planetary systems: discs and close-in planetesimals

λ flux

  • Spectroscopic signatures of accreted metals (~45%
  • f WDs, Wilson et al. 2019) and possible planet

(Gänsicke et al. 2019)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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White dwarf planetary systems: discs and close-in planetesimals

λ flux λ flux

  • Spectroscopic signatures of accreted metals (~45%
  • f WDs, Wilson et al. 2019) and possible planet

(Gänsicke et al. 2019)

  • Dust discs detected through IR excesses (~1.5% of

WDs, Wilson et al. 2019)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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White dwarf planetary systems: discs and close-in planetesimals

λ flux λ flux λ flux

  • Spectroscopic signatures of accreted metals (~45%
  • f WDs, Wilson et al. 2019) and possible planet

(Gänsicke et al. 2019)

  • Dust discs detected through IR excesses (~1.5% of

WDs, Wilson et al. 2019)

  • Gas discs detected through Keplerian emission

features (~0.1% of WDs, Gänsicke et al. 2007, Manser et al. 2020)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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White dwarf planetary systems: discs and close-in planetesimals

time flux λ flux λ flux λ flux

  • Spectroscopic signatures of accreted metals (~45%
  • f WDs, Wilson et al. 2019) and possible planet

(Gänsicke et al. 2019)

  • Dust discs detected through IR excesses (~1.5% of

WDs, Wilson et al. 2019)

  • Gas discs detected through Keplerian emission

features (~0.1% of WDs, Gänsicke et al. 2007, Manser et al. 2020)

  • Transits of disintegrating asteroids (2 known,

Vanderburg et al. 2015, Vanderbosch et al. 2019)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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White dwarf planetary systems: discs and close-in planetesimals

time flux λ flux λ flux λ flux time line strength and shape

  • Spectroscopic signatures of accreted metals (~45%
  • f WDs, Wilson et al. 2019) and possible planet

(Gänsicke et al. 2019)

  • Dust discs detected through IR excesses (~1.5% of

WDs, Wilson et al. 2019)

  • Gas discs detected through Keplerian emission

features (~0.1% of WDs, Gänsicke et al. 2007, Manser et al. 2020)

  • Transits of disintegrating asteroids (2 known,

Vanderburg et al. 2015, Vanderbosch et al. 2019)

  • Spectral signatures of non-transiting asteroids

(1 known, Manser,…, Mustill et al. 2019)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Unifying idea:

Material is driven towards the WD on highly-eccentric orbits by large bodies in the outer system. It undergoes orbital circularisation, pulverisation and vaporisation, forms a close-in disc, and ultimately accretes onto the WD. Reviews: Farihi 2016 (observations), Veras 2016 (theory)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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How and why does material get close to the white dwarf?

Mustill & Villaver 2012

Stellar radius

AGB star loses mass (50% for 1M⊙) and increases in radius (1au for 1M⊙)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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How and why does material get close to the white dwarf?

Planets escaped

Mustill & Villaver 2012

Stellar radius

Stellar mass loss causes

  • rbit expansion to conserve

L = [GM★a(1 - e2)]1/2 AGB star loses mass (50% for 1M⊙) and increases in radius (1au for 1M⊙)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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How and why does material get close to the white dwarf?

Planets engulfed Planets escaped

Mustill & Villaver 2012

Stellar radius

Stellar mass loss causes

  • rbit expansion to conserve

L = [GM★a(1 - e2)]1/2 Stellar radius expansion strengthens tides AGB star loses mass (50% for 1M⊙) and increases in radius (1au for 1M⊙)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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3.0 2.5 2.0 1.5 1.0 0.5 0.0

Mass of Star [Solar Mass]

10

  • 3

0.01 0.1 1 10 100 103 100 10 1 0.1 0.01

Semi-Major Axis [Astronomical Units (AU)] Planet Mass [Earth Mass]

exoplanets.org | 3/28/2017

⊕ ☿ ♀ ♂ ♃ ♄ ⛢ ♆

Present-day Solar radius

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3.0 2.5 2.0 1.5 1.0 0.5 0.0

Mass of Star [Solar Mass]

10

  • 3

0.01 0.1 1 10 100 103 100 10 1 0.1 0.01

Semi-Major Axis [Astronomical Units (AU)] Planet Mass [Earth Mass]

exoplanets.org | 3/28/2017

Survive engulfment Engulfed by giant star

⊕ ☿ ♀ ♂ ♃ ♄ ⛢ ♆

Present-day Solar radius Mustill & Villaver 2012 survival limit

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WDs observed typically descend from single stars slightly more massive than Sun

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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WDs observed typically descend from single stars slightly more massive than Sun

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Few in number

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WDs observed typically descend from single stars slightly more massive than Sun

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Few in number Have not evolved

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WDs observed typically descend from single stars slightly more massive than Sun

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Few in number Have not evolved Typical exoplanet surveys

Koester et al 2014

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Asteroid delivery by destabilised planetary systems

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Asteroid delivery by destabilised planetary systems

  • Loss of stellar mass also

increase the planet:star mass

  • ratio. This ratio sets the

timescale and strength of planet–planet and planet– asteroid interactions

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Asteroid delivery by destabilised planetary systems

  • Loss of stellar mass also

increase the planet:star mass

  • ratio. This ratio sets the

timescale and strength of planet–planet and planet– asteroid interactions

  • E.g., the Hill spheres of planets

expand: rH = a (Mpl/3M★)1/3

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Asteroid delivery by destabilised planetary systems

  • Loss of stellar mass also

increase the planet:star mass

  • ratio. This ratio sets the

timescale and strength of planet–planet and planet– asteroid interactions

  • E.g., the Hill spheres of planets

expand: rH = a (Mpl/3M★)1/3

  • This destabilises formerly

stable systems (Debes & Sigurdsson 2002, Mustill et al., 2014, 2018)

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Asteroid delivery by destabilised planetary systems

  • Loss of stellar mass also

increase the planet:star mass

  • ratio. This ratio sets the

timescale and strength of planet–planet and planet– asteroid interactions

  • E.g., the Hill spheres of planets

expand: rH = a (Mpl/3M★)1/3

  • This destabilises formerly

stable systems (Debes & Sigurdsson 2002, Mustill et al., 2014, 2018)

Mustill et al 2014 Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Asteroid delivery by destabilised planetary systems

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Frewen & Hansen (2014) showed that an eccentric, low-mass (super-Earth or Neptune) planet is an efficient deliverer of material, but did not look at the origin of the eccentricity

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Asteroid delivery by destabilised planetary systems

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Frewen & Hansen (2014) showed that an eccentric, low-mass (super-Earth or Neptune) planet is an efficient deliverer of material, but did not look at the origin of the eccentricity

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Asteroid delivery by destabilised planetary systems

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Frewen & Hansen (2014) showed that an eccentric, low-mass (super-Earth or Neptune) planet is an efficient deliverer of material, but did not look at the origin of the eccentricity

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Asteroid delivery by destabilised planetary systems

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

Frewen & Hansen (2014) showed that an eccentric, low-mass (super-Earth or Neptune) planet is an efficient deliverer of material, but did not look at the origin of the eccentricity

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Asteroid delivery by destabilised planetary systems

AGB tip instability

Mustill et al 2018

Planets 1-30M⊕ Planetesimals

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11

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Asteroid delivery by destabilised planetary systems

Red: inner belt particles Blue: outer belt particles

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11 Mustill et al 2018

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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11 Maldonado, Villaver, Mustill et al., in prep

Using real systems as a template: most 2-planet systems remain stable

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Evolution after main sequence (§4) Evolution as white dwarf in Galactic field (§5) Evolution along main sequence in Galactic field (§3) Evolution in cluster (§2) time

t = 0: after gas disc dissipation and planet formation t = 100Myr: leave cluster t = 11Gyr: leave main sequence t = 12.5Gyr: AGB tip, white dwarf forms

Cluster N-body with NBODY6++ Planetary N-body with REBOUND Coupling with LPS/AMUSE Galactic tide and stellar encounter rate based on present Solar orbit Planetary N-body with MERCURY including Galactic tides and encounters Extrapolation along whole main-sequence lifetime Planetary N-body with MERCURY including stellar evolution with SSE Estimation of effects

  • f Galactic tide and

encounters on the white dwarf system

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11 Veras,…, Mustill et al., submitted

Using real systems as a template: Solar System with exterior planetesimal disc

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Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11 Veras,…, Mustill et al., submitted

Using real systems as a template: Solar System with exterior planetesimal disc remains mostly stable

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Summary

Metals accreted into WD atmospheres provide a means to determine the elemental compositions of exoplanets and asteroids White dwarfs also show circumstellar gas and dust discs, and transiting and non-transiting asteroids Asteroidal or planetary material is scattered from the outer system that survives AGB evolution, circularised and processed through dust and gas discs to accrete onto the star This material can be delivered by planets that survive stellar

  • evolution. Low mass planets are most efficient, and provide the

delivery over extended timescales, matching observed trends However, identifying the genuine configurations of planetary systems responsible is challenging and ongoing

Alexander Mustill (Lund University) — Compact Objects For All — 2020-02-11