An Isolated White Dwarf with 317 s Rotation and Magnetic Emission

Reding, Joshua S.; Hermes, J. J.; Vanderbosch, Zachary P.; Dennihy, E.; Kaiser, Bastian; Mace, Charlie; Dunlap, B. H.; Clemens, J. C.

doi:10.3847/1538-4357/ab8239

Cited by 44 publications

(70 citation statements)

References 62 publications

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“…Figure 2 shows the spin-up of a 0.6 M ⊙ white dwarf for different total accretion rates as a function of the spin-up efficiency. For accreted masses exceeding 10 −5 M ⊙ we find rotation periods ranging from several minutes, as recently observed (Reding et al 2020), to a few hours, much shorter than the assumed initial rotation rate of 1-3 days (Hermes et al 2017). At the same time, the spin periods reached remain longer than the spin period estimated by Isern et al (2017) for satu- Final white dwarf spin period ( WD ) against the spin-up efficiency parameter ( ), for four different accreted masses, in M ⊙ , namely 10 −6 , 10 −5 , 10 −4 and 10 −3 and two initial spin periods.…”

Section: Spin-up Of the White Dwarfsupporting

confidence: 82%

Magnetic dynamos in white dwarfs – II. Relating magnetism and pollution

Schreiber

Belloni

Gänsicke

et al. 2021

Monthly Notices of the Royal Astronomical Society: Letters

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We investigate whether the recently suggested rotation and crystallization driven dynamo can explain the apparent increase of magnetism in old metal polluted white dwarfs. We find that the effective temperature distribution of polluted magnetic white dwarfs is in agreement with most/all of them having a crystallizing core and increased rotational velocities are expected due to accretion of planetary material which is evidenced by the metal absorption lines. We conclude that a rotation and crystallization driven dynamo offers not only an explanation for the different occurrence rates of strongly magnetic white dwarfs in close binaries, but also for the high incidence of weaker magnetic fields in old metal polluted white dwarfs.

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Section: Spin-up Of the White Dwarfsupporting

confidence: 82%

Magnetic dynamos in white dwarfs – II. Relating magnetism and pollution

Schreiber

Belloni

Gänsicke

et al. 2021

Monthly Notices of the Royal Astronomical Society: Letters

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“…No such correlation could be claimed although their observations did not allow to rule out the hypothesis either. In contrast, photometric variability has been linked to magnetic white dwarfs (Lawrie et al 2013;Brinkworth et al 2013;Reding et al 2020;Gänsicke et al 2020). In those cases the light intensity is thought to be inhomogeneous across the stellar surface, e.g.…”

Section: Discussionmentioning

confidence: 99%

Horizontal spreading of planetary debris accreted by white dwarfs

Cunningham

Tremblay

Bauer

et al. 2021

Monthly Notices of the Royal Astronomical Society

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White dwarfs with metal-polluted atmospheres have been studied widely in the context of the accretion of rocky debris from evolved planetary systems. One open question is the geometry of accretion and how material arrives and mixes in the white dwarf surface layers. Using the 3D radiation-hydrodynamics code CO5BOLD, we present the first transport coefficients in degenerate star atmospheres which describe the advection-diffusion of a passive scalar across the surface-plane. We couple newly derived horizontal diffusion coefficients with previously published vertical diffusion coefficients to provide theoretical constraints on surface spreading of metals in white dwarfs. Our grid of 3D simulations probes the vast majority of the parameter space of convective white dwarfs, with pure-hydrogen atmospheres in the effective temperature range 6000–18 000 K and pure-helium atmospheres in the range 12 000–34 000 K. Our results suggest that warm hydrogen-rich atmospheres (DA; ≳ 13 000 K) and helium-rich atmospheres (DB, DBA; ≳ 30 000 K) are unable to efficiently spread the accreted metals across their surface, regardless of the time dependence of accretion. This result may be at odds with the current non-detection of surface abundance variations at white dwarfs with debris discs. For cooler hydrogen- and helium-rich atmospheres, we predict a largely homogeneous distribution of metals across the surface within a vertical diffusion timescale. This is typically less than 0.1 per cent of disc lifetime estimates, a quantity which is revisited in this paper using the overshoot results. These results have relevance for studies of the bulk composition of evolved planetary systems and models of accretion disc physics.

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“…In the latter case, the white dwarf remnant is expected to be highly magnetised 6,7 due to the strong dynamo that may arise during the merger, and rapidly rotating due to conservation of the orbital angular momentum of the binary 8 . Here we report the discovery of a white dwarf, ZTF J190132.9+145808.7, which presents all these properties, but to an extreme: a rotation period of 6.94 minutes, one of the shortest measured for an isolated white dwarf 9,10 , a magnetic field ranging between 600 MG and 900 MG over its surface, one of the highest fields ever detected on a white dwarf 11 , and a stellar radius of 1810 km, slightly larger than the radius of the Moon. Such a small radius implies the star's mass is the closest ever detected to the white dwarf maximum mass, or Chandrasekhar mass 12 .…”

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confidence: 88%

A moon-sized, highly magnetised and rapidly rotating white dwarf may be headed toward collapse

Caiazzo

Burdge

Fuller

et al. 2020

Preprint

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White dwarfs represent the last stage of evolution for low and intermediate-mass stars (below about 8 times the mass of our Sun), and like their stellar progenitors, they are often found in binaries. If the orbital period of the binary is short enough, energy losses from gravitational wave radiation can shrink the orbit until the two white dwarfs come into contact and merge. Depending on the masses of the coalescing white dwarfs, the merger can lead to a supernova of type Ia, or it can give birth to a massive white dwarf. In the latter case, the white dwarf remnant is expected to be highly magnetised due to the strong dynamo that may arise during the merger, and rapidly rotating due to conservation of the orbital angular momentum of the binary. Here we report the discovery of a white dwarf, ZTF J190132.9+145808.7, which presents all these properties, but to an extreme: a rotation period of 6.94 minutes, one of the shortest measured for an isolated white dwarf, a magnetic field ranging between 600 MG and 900 MG over its surface, one of the highest fields ever detected on a white dwarf, and a stellar radius of 1810 km, slightly larger than the radius of the Moon. Such a small radius implies the star's mass is the closest ever detected to the white dwarf maximum mass, or Chandrasekhar mass. In fact, as the white dwarf cools and its composition stratifies, it may become unstable and collapse due to electron capture, exploding into a thermonuclear supernova or collapsing into a neutron star. Neutron stars born in this fashion could account for 10% of their total population.

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An Isolated White Dwarf with 317 s Rotation and Magnetic Emission

Abstract: OpenBU http://open.bu.edu Astronomy BU Open Access Articles An isolated white dwarf with 317 s rotation and magnetic emission This work was made openly accessible by BU Faculty. Please share how this access benefits you. Your story matters.

Cited by 44 publications

References 62 publications

Magnetic dynamos in white dwarfs – II. Relating magnetism and pollution

Magnetic dynamos in white dwarfs – II. Relating magnetism and pollution

Horizontal spreading of planetary debris accreted by white dwarfs

A moon-sized, highly magnetised and rapidly rotating white dwarf may be headed toward collapse

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