Polluted white dwarfs: constraints on the origin and geology of exoplanetary material

Harrison, John; Bonsor, Amy; Madhusudhan, Nikku

doi:10.1093/mnras/sty1700

Cited by 124 publications

(149 citation statements)

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“…We verify that neutral atomic Fe is the dominant Fe species using equilibrium chemistry calculations computed with the HSC Chemistry software (version 8) (e.g. Pasek et al 2005;Bond et al 2010;Elser et al 2012;Madhusudhan 2012;Moriarty et al 2014;Harrison et al 2018). These calculations assume solar elemental abundances (Asplund et al 2009) and include the same species as Harrison et al (2018) plus gaseous, solid, neutral and ionic molecules and atomic forms of Fe, Ti, V, Cr and Mg. Figure 4 shows the equilibrium abundances of several neutral gaseous Fe species between 1000-3000 K at a pressure of 1 mbar nominally corresponding to the optical photosphere.…”

Section: Model Spectramentioning

confidence: 99%

“…Pasek et al 2005;Bond et al 2010;Elser et al 2012;Madhusudhan 2012;Moriarty et al 2014;Harrison et al 2018). These calculations assume solar elemental abundances (Asplund et al 2009) and include the same species as Harrison et al (2018) plus gaseous, solid, neutral and ionic molecules and atomic forms of Fe, Ti, V, Cr and Mg. Figure 4 shows the equilibrium abundances of several neutral gaseous Fe species between 1000-3000 K at a pressure of 1 mbar nominally corresponding to the optical photosphere. At the equilibrium temperature of WASP-121 b (∼2400 K), neutral atomic Fe is the dominant form of Fe and should therefore be the most easily detected (also see Kitzmann et al 2018;Lothringer et al 2018).…”

Section: Model Spectramentioning

confidence: 99%

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Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Cabot

Madhusudhan

Welbanks

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The class of ultra-hot Jupiters comprises giant exoplanets undergoing intense irradiation from their host stars. They have proved to be a particularly interesting population for their orbital and atmospheric properties. One such planet, WASP-121 b, is in a highly misaligned orbit close to its Roche limit, and its atmosphere exhibits a thermal inversion. These properties make WASP-121 b an interesting target for additional atmospheric characterization. In this paper, we present analysis of archival high-resolution optical spectra obtained during transits of WASP-121 b. Artifacts from the Rossiter-McLaughlin effect and Center-to-Limb Variation are deemed negligible. However, we discuss scenarios where these effects warrant more careful treatment by modeling the WASP-121 system and varying its properties. We report a new detection of atmospheric absorption from Hα in the planet with a transit depth of 1.87 ± 0.11%. We further confirm a previous detection of the Na I doublet, and report a new detection of Fe I via cross-correlation with a model template. We attribute the Hα absorption to an extended Hydrogen atmosphere, potentially undergoing escape, and the Fe I to equilibrium chemistry at the planetary photosphere. These detections help to constrain the composition and chemical processes in the atmosphere of WASP-121 b.

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Section: Model Spectramentioning

confidence: 99%

Section: Model Spectramentioning

confidence: 99%

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Cabot

Madhusudhan

Welbanks

et al. 2020

Monthly Notices of the Royal Astronomical Society

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100

106

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“…Establishing a compositional link between crater ejecta and metals found in white dwarfs is another important extension of these results. If observational distinctions between detections of the bulk remains of an exo-asteroid versus the crustal material of an exo-planet can be enhanced (Harrison et al 2018;Hollands et al 2018;Bonsor et al 2020), then understanding the mass and dynamical pathways of impact ejecta would become more important. Tracing the chemistry and dynamics back to planetary system formation along the early main sequence phase (Harrison et al 2018;Bonsor et al 2020) has the potential to link planetary architecture with instabilities, bombardments and observed accretion rates.…”

Section: Discussionmentioning

confidence: 99%

“…Some white dwarfs contain at least ten different observable exoplanetary metals (e.g. Dufour et al 2012;Melis & Dufour 2017;Swan et al 2019;Xu et al 2019), and about two dozen white dwarfs currently host at least five metals (Harrison et al 2018;Hollands et al 2018). In each case, because of spectroscopic limitations, we obtain only a partial snapshot of the bulk chemical composition of progenitor exoplanetary material.…”

Section: Fates Of Planetary Systemsmentioning

confidence: 99%

Generating metal-polluting debris in white dwarf planetary systems from small-impact crater ejecta

Veras

Kurosawa

2020

Monthly Notices of the Royal Astronomical Society

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Metal pollution in white dwarf photospheres originates from the accretion of some combination of planets, moons, asteroids, comets, boulders, pebbles and dust. When large bodies reside in dynamically stagnant locations -unable themselves to pollute nor even closely approach the white dwarf -then smaller reservoirs of impact debris may become a complementary or the primary source of metal pollutants. Here, we take a first step towards exploring this possibility by computing limits on the recoil mass that escapes the gravitational pull of the target object following a single impact onto an atmosphere-less surface. By considering vertical impacts only with the full-chain analytical prescription from Kurosawa & Takada (2019), we provide lower bounds for the ejected mass for basalt, granite, iron and water-rich target objects across the radii range 10 0−3 km. Our use of the full-chain prescription as opposed to physical experiments or hydrocode simulations allows us to quickly sample a wide range of parameter space appropriate to white dwarf planetary systems. Our numerical results could be used in future studies to constrain freshly-generated small debris reservoirs around white dwarfs given a particular planetary system architecture, bombardment history, and impact geometries.

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“…Some bodies also show evidence for differentiation, posing questions about collisional processing (e.g. Hollands et al 2018;Harrison et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Near-infrared variability in dusty white dwarfs: tracing the accretion of planetary material

Rogers

Bonsor

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The inwards scattering of planetesimals towards white dwarfs is expected to be a stochastic process with variability on human time-scales. The planetesimals tidally disrupt at the Roche radius, producing dusty debris detectable as excess infrared emission. When sufficiently close to the white dwarf, this debris sublimates and accretes on to the white dwarf and pollutes its atmosphere. Studying this infrared emission around polluted white dwarfs can reveal how this planetary material arrives in their atmospheres. We report a near-infrared monitoring campaign of 34 white dwarfs with infrared excesses with the aim to search for variability in the dust emission. Time series photometry of these white dwarfs from the United Kingdom Infrared Telescope (Wide Field Camera) in the J, H and K bands were obtained over baselines of up to three years. We find no statistically significant variation in the dust emission in all three near-infrared bands. Specifically, we can rule out variability at ∼ 1.3% for the 13 white dwarfs brighter than 16th mag in K band, and at ∼ 10% for the 32 white dwarfs brighter than 18th mag over time-scales of three years. Although to date two white dwarfs, SDSS J095904.69−020047.6 and WD 1226+110, have shown K band variability, in our sample we see no evidence of new K band variability at these levels. One interpretation is that the tidal disruption events which lead to large variabilities are rare, occur on short time-scales, and after a few years the white dwarfs return to being stable in the near-infrared.

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Polluted white dwarfs: constraints on the origin and geology of exoplanetary material

Cited by 124 publications

References 83 publications

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Generating metal-polluting debris in white dwarf planetary systems from small-impact crater ejecta

Near-infrared variability in dusty white dwarfs: tracing the accretion of planetary material

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