Formation of eccentric gas discs from sublimating or partially disrupted asteroids orbiting white dwarfs

Trevascus, David; Price, Daniel J.; Nealon, Rebecca; Liptai, David; Manser, Christopher J.; Veras, Dimitri

doi:10.1093/mnrasl/slab043

Cited by 23 publications

(11 citation statements)

References 58 publications

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“…Five per cent of infrared-bright debris discs around white dwarfs are observed to host an additional gaseous component in emission (Gänsicke et al 2006;Manser et al 2020), identified via the doublepeaked Ca 8600 Å triplet emission profiles produced by a flat, photo-ionised Keplerian disc (Horne & Marsh 1986;Melis et al 2010;Kinnear 2011;Gänsicke et al 2019). The origin of these gaseous components is uncertain, but current mechanisms include: runaway sublimation of dust at the inner edge of the debris disc due to angular momentum conservation (Rafikov 2011;Metzger et al 2012), a collisional cascade of rocky bodies being ground down into dust and gas (Kenyon & Bromley 2017a,b), collisions produced via a tidal stream of planetary debris impacting on a pre-existing disc (Jura 2008;Malamud et al 2021), and a disc-embedded planetesimal that survived the tidal disruption process, inducing the production of gas through collisions or sublimation (Manser et al 2019;Trevascus et al 2021). Recent observations show that variability of the infrared excess from debris discs is common (Xu & Jura 2014;Xu et al 2018;Swan et al 2019;Wang et al 2019), and it has been proposed that the observed variations are due to the production and destruction of dust via planetesimal collisions which could also produce observable gaseous material (Farihi et al 2018;Swan et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349–2305 using Doppler tomography

Manser

Dennihy

Gänsicke

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The presence of planetary material in white dwarf atmospheres, thought to be accreted from a dusty debris disc produced via the tidal disruption of a planetesimal, is common. Approximately five per cent of these discs host a co-orbital gaseous component detectable via emission from atomic transitions – usually the 8600 Å Ca ii triplet. These emission profiles can be highly variable in both morphology and strength. Furthermore, the morphological variations in a few systems have been shown to be periodic, likely produced by an apsidally precessing asymmetric disc. Of the known gaseous debris discs, that around HE 1349–2305 has the most rapidly evolving emission line morphology, and we present updated spectroscopy of the Ca ii triplet of this system. The additional observations show that the emission line morphologies vary periodically and consistently, and we constrain the period to two aliases of 459 ± 3 d and 502 ± 3 d. We produce images of the Ca ii triplet emission from the disc in velocity space using Doppler tomography – only the second such imaging of a white dwarf debris disc. We suggest that the asymmetric nature of these velocity images is generated by gas moving on eccentric orbits with radially-dependent excitation conditions via photo-ionisation from the white dwarf. We also obtained short-cadence (≃ 4 min) spectroscopy to search for variability on the time-scale of the disc’s orbital period (≃ hours) due to the presence of a planetesimal, and rule out variability at a level of ≃ 1.4 per cent.

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Section: Introductionmentioning

confidence: 99%

Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349–2305 using Doppler tomography

Manser

Dennihy

Gänsicke

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…The sublimated material from an asteroid approaching a white dwarf on an extremely eccentric orbit could quickly accrete onto the white dwarf, or form part of a gaseous debris disc (Trevascus et al 2021). The white dwarf SDSS J1228+1040 is observed with an extremely dense planetesimal orbiting inside a debris disc with a gaseous component expanding out to ∼ 1.2𝑅 (Gänsicke et al 2006;Manser et al 2019).…”

Section: Sublimated Materialsmentioning

confidence: 99%

White dwarf planetary debris dependence on physical structure distributions within asteroid belts

McDonald,

Veras

2021

Preprint

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White dwarfs which exhibit transit signatures of planetary debris and accreted planetary material provide exceptional opportunities to probe the material composition and dynamical structure of planetary systems. Although previous theoretical work investigating the role of minor body disruption around white dwarfs has focussed on spherical bodies, Solar System asteroids can be more accurately modelled as triaxial ellipsoids. Here we present an analytical framework to identify the type of disruption (tidal fragmentation, total sublimation or direct impact) experienced by triaxial asteroids approaching white dwarfs on extremely eccentric (𝑒 ∼ 1) orbits. This framework is then used to identify the outcomes for simplified Main belt analogues of 100 bodies across five different white dwarf temperatures. We also present an empirical relationship between cooling age and effective temperature for both DA and DB white dwarfs to identify the age of the white dwarfs considered here. We find that using a purely spherical shape model can underestimate the physical size and radial distance at which an asteroid is subjected to complete sublimation, and these differences increase with greater elongation of the body. Contrastingly, fragmentation always occurs in the largest semi-axis of a body and so can be modelled by a sphere of that radius. Both fragmentation and sublimation are greatly affected by the body's material composition, and hence by the composition of their progenitor asteroid belts. The white dwarf temperature, and hence cooling age, can affect the expected debris distribution: higher temperatures sublimate large elongated asteroids, and cooler temperatures accommodate more direct impacts.

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“…The analytic solutions only result in fallback for e < 1.02. Trevascus et al 2021;Wang et al 2021). We use ∼ 10 6 particles to model the disruption of a solar-like, γ = 5/3 polytrope (with M = M and R * = R ) by a 10 6 M supermassive black hole.…”

Section: Simulation Setupmentioning

confidence: 99%

The Eccentric Nature of Eccentric Tidal Disruption Events

Cufari,

Coughlin,

Nixon

2021

Preprint

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Upon entering the tidal sphere of a supermassive black hole, a star is ripped apart by tides and transformed into a stream of debris. The ultimate fate of that debris, and the properties of the bright flare that is produced and observed, depends on a number of parameters, including the energy of the center of mass of the original star. Here we present the results of a set of smoothed particle hydrodynamics simulations in which a 1 M , γ = 5/3 polytrope is disrupted by a 10 6 M supermassive black hole. Each simulation has a pericenter distance of r p = r t (i.e., β ≡ r t /r p = 1 with r t the tidal radius), and we vary the eccentricity e of the stellar orbit from e = 0.8 up to e = 1.20 and study the nature of the fallback of debris onto the black hole and the long-term fate of the unbound material. For simulations with eccentricities e 0.98, the fallback curve has a distinct, three-peak structure that is induced by self-gravity. For simulations with eccentricities e 1.06, the core of the disrupted star reforms following its initial disruption. Our results have implications for, e.g., tidal disruption events produced by supermassive black hole binaries.

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Formation of eccentric gas discs from sublimating or partially disrupted asteroids orbiting white dwarfs

Cited by 23 publications

References 58 publications

Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349–2305 using Doppler tomography

Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349–2305 using Doppler tomography

White dwarf planetary debris dependence on physical structure distributions within asteroid belts

The Eccentric Nature of Eccentric Tidal Disruption Events

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