A massive white-dwarf merger product before final collapse

Gvaramadze, V. V.; Gräfener, G.; Langer, N.; Maryeva, O. V.; Kniazev, A. Y.; Москвитин, А. С.; Spiridonova, O. I.

doi:10.1038/s41586-019-1216-1

Cited by 58 publications

(132 citation statements)

References 45 publications

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“…Contrary to Gvaramadze et al (2019), our model indicates that WD J005311 is not a super-Chandrasekhar-mass system and will neither explode as a supernova Ia nor collapse into a neutron star. The inferred fast spin and strong magnetic field are still consistent with the WD merger origin as proposed by Gvaramadze et al (2019).…”

Section: Discussioncontrasting

confidence: 75%

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The Optically Thick Rotating Magnetic Wind from a Massive White Dwarf Merger Product

Kashiyama

Fujisawa

Shigeyama

2019

ApJ

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WD J005311 is a newly identified white dwarf (WD) in a mid-infrared nebula. The spectroscopic observation indicates the existence of a neon-enriched carbon/oxygen wind with a terminal velocity of v ∞,obs ∼ 16, 000 km s −1 and a mass loss rate ofṀ obs ∼ 3.5 × 10 −6 M ⊙ yr −1 . Here we consistently explain the properties of WD J005311 using a newly constructed wind solution, where the optically thick outflow is launched from the carbon burning shell on an oxygen-neon core and accelerated by the rotating magnetic field to become supersonic and unbound well below the photosphere. Our model implies that WD J005311 has a mass of M * ∼ 1.1-1.3 M ⊙ , a magnetic field of B * ∼ (2-5) × 10 7 G, and a spin angular frequency of Ω ∼ 0.2-0.5 s −1 . The large magnetic field and fast spin support the carbon-oxygen WD merger origin. WD J005311 will neither explode as a type Ia supernova nor collapse into a neutron star. If the wind continues to blow another few kyr, WD J005311 will spin down significantly and join to the known sequence of slowly-rotating magnetic WDs. Otherwise it may appear as a fast-spinning magnetic WD and could be a new high energy source.• The effective temperature of WD J005311 is T eff = 211, 000 +40,000 −23,000 K.• The distance to WD J005311 is d = 3.07 +0.34 −0.28 kpc and the bolometric luminosity is calculated as log(L bol /L ⊙ ) = 4.60 ± 0.14.• The photospheric radius is estimated to be r ph,obs = 0.15 ± 0.04 R ⊙ .• The chemical composition of the wind is dominated by carbon and oxygen (X C = 0.2 ± 0.1 and X O = 0.8 ± 0.1).

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Section: Discussioncontrasting

confidence: 75%

“…Recently Gvaramadze et al (2019) reported observation of an extremely hot WD in a mid-infrared nebula J005311 that exhibits some features predicted for a merger product. In addition, the spectroscopic analysis indicates the existence of a peculiar wind, which might give a clue to the fate of this object.…”

Section: Introductionmentioning

confidence: 94%

The Optically Thick Rotating Magnetic Wind from a Massive White Dwarf Merger Product

Kashiyama

Fujisawa

Shigeyama

2019

ApJ

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“…Our analysis of the envelope and interior indicates that the total hydrogen and helium mass fractions must be several orders of magnitude lower than predictions of single star evolution 10 : less than 10 −9.5 and 10 −7.0 , respectively. Due to the fast kinematics (129 ± 5 km s −1 relative to the local standard of rest), large mass, and peculiar envelope composition, we argue that WD J0551+4135 is consistent with formation from the merger of two white dwarfs in a tight binary system [11][12][13][14] .WD J0551+4135 was identified as a candidate high-mass white dwarf 15 from its location in the Gaia Hertzsprung-Russell diagram 16 (Fig. 1).…”

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confidence: 88%

An ultra-massive white dwarf with a mixed hydrogen–carbon atmosphere as a likely merger remnant

et al. 2020

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White dwarfs are dense, cooling stellar embers consisting mostly of carbon and oxygen 1 , or oxygen and neon (with a few percent carbon) at higher initial stellar masses 2 . These stellar cores are enveloped by a shell of helium which in turn is usually surrounded by a layer of hydrogen, generally prohibiting direct observation of the interior composition. However, 1 arXiv:2003.00028v1 [astro-ph.SR] 28 Feb 2020 carbon is observed at the surface of a sizeable fraction of white dwarfs 3, 4 , sometimes with traces of oxygen, and it is thought to be dredged-up from the core by a deep helium convection zone 5, 6 . In these objects only traces of hydrogen are found 7, 8 as large masses of hydrogen are predicted to inhibit hydrogen/helium convective mixing within the envelope 9 . We report the identification of WD J055134.612+413531.09, an ultra-massive (1.14 M ) white dwarf with a unique hydrogen/carbon mixed atmosphere (C/H = 0.15 in number ratio). Our analysis of the envelope and interior indicates that the total hydrogen and helium mass fractions must be several orders of magnitude lower than predictions of single star evolution 10 : less than 10 −9.5 and 10 −7.0 , respectively. Due to the fast kinematics (129 ± 5 km s −1 relative to the local standard of rest), large mass, and peculiar envelope composition, we argue that WD J0551+4135 is consistent with formation from the merger of two white dwarfs in a tight binary system [11][12][13][14] .WD J0551+4135 was identified as a candidate high-mass white dwarf 15 from its location in the Gaia Hertzsprung-Russell diagram 16 (Fig. 1). The Gaia parallax places WD J0551+4135 at 46.45 ± 0.15 pc away from the Sun. Compared to most other white dwarfs of the same G BP − G RP colour, WD J0551+4135 is fainter in absolute magnitude, signifying a relatively small radius, and thus a large mass given the mass-radius relation of white dwarfs whose structure is dominated by electron degeneracy 17 .− log(1 − m r /M wd ) = 4 (where m r is the mass enclosed within a sphere of radius r), the models are almost indistinguishable. Therefore the degree of oxygen dredge-up is not found to depend upon the core-composition, and so the atmospheric non-detection of oxygen cannot be used to test the evolutionary history. 6

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“…This is similar to the magnetar powering function (t −2 ) and hence would likely result in a similar lightcurve. Schwab et al (2016) suggest another possible channel to produce a rapidly rotating neutron star remnant is through the merger of two WDs, potentially avoiding thermonuclear runaway and creating a massive, rapidly rotating WD that will likely collapse (Gvaramadze et al 2019).…”

Section: Explosion Mechanism and Scenariomentioning

confidence: 99%

SN2018kzr: A Rapidly Declining Transient from the Destruction of a White Dwarf

McBrien

Smartt

Chen

et al. 2019

ApJL

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We present SN2018kzr, the fastest declining supernova-like transient, second only to the kilonova, AT2017gfo. SN2018kzr is characterized by a peak magnitude of M r = −17.98, peak bolometric luminosity of ∼1.4 × 10 43 erg s −1 and a rapid decline rate of 0.48 ± 0.03 mag d -1 in the r band. The bolometric luminosity evolves too quickly to be explained by pure 56 Ni heating, necessitating the inclusion of an alternative powering source. Incorporating the spin-down of a magnetized neutron star adequately describes the lightcurve and we estimate a small ejecta mass of M ej = 0.10 ± 0.05 M . Our spectral modelling suggests the ejecta is composed of intermediate mass elements including O, Si and Mg and trace amounts of Fe-peak elements, which disfavours a binary neutron star merger. We discuss three explosion scenarios for SN2018kzr, given the low ejecta mass, intermediate mass element composition and the high likelihood of additional powering -core collapse of an ultra-stripped

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A massive white-dwarf merger product before final collapse

Cited by 58 publications

References 45 publications

The Optically Thick Rotating Magnetic Wind from a Massive White Dwarf Merger Product

The Optically Thick Rotating Magnetic Wind from a Massive White Dwarf Merger Product

An ultra-massive white dwarf with a mixed hydrogen–carbon atmosphere as a likely merger remnant

SN2018kzr: A Rapidly Declining Transient from the Destruction of a White Dwarf

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