Double White Dwarf Merger Products among High-mass White Dwarfs

Cheng, Sihao; Cummings, Jeffrey D.; Ménard, Brice; Toonen, Silvia

doi:10.3847/1538-4357/ab733c

Cited by 59 publications

(59 citation statements)

References 80 publications

(80 reference statements)

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“…Previous works were mainly focused on extrapolating the orbital distribution of premerger systems (e.g., Brown et al 2016;Maoz et al 2018), which currently provides no or low mass resolution and large uncertainties. The merger rate translated from the fraction of merger products in Cheng et al (2019b) adds significant mass resolution and precision to previous measurements, and it is shown to be close to binary simulation results (Figure 2).…”

Section: How Frequently Do Two White Dwarfs Merge?supporting

confidence: 77%

“…Estimates of the double-WD merger rate as a function of total mass, from both observational and theoretical sides. This figure is reproduced from the Figure 4 in Cheng et al (2019b). > 1.4 M is a third to a half of the type-Ia supernova rate measured for Milky-Way-like galaxies (Li et al 2011).…”

Section: How Frequently Do Two White Dwarfs Merge?mentioning

confidence: 79%

“…Because double-WD merger products experience additional binary evolution, their true ages are younger than their photometric isochrone ages. To get rid of the influence of the cooling anomaly described in the previous section, Cheng et al (2019b) selected only high-mass white dwarfs above the Q branch and used their transverse velocity distribution to infer the fraction of merger products. Thanks to the much larger sample size than what Wegg & Phinney (2012) used in a previous study with similar method, Cheng et al (2019b) found clear velocity excess that corresponds to about 20 ± 6% of high-mass white dwarfs (0.8-1.3 M ) being double-WD merger products.…”

Section: What Are the Origins Of High-mass White Dwarfs?mentioning

confidence: 99%

See 2 more Smart Citations

Two delays in white dwarf evolution revealed byGaia

Cheng

2019

Proc. IAU

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By comparing two age indicators of high-mass white dwarfs (WDs) derived from Gaia data, two discoveries have been made recently: one is the existence of a cooling anomaly that produces the Q branch structure on the Hertzsprung–Russell diagram, and the other is the existence of high-mass WDs as double-WD merger products. The former poses a challenge for WD cooling models, and the latter has implications on binary evolution and type-Ia supernovae.

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Section: How Frequently Do Two White Dwarfs Merge?supporting

confidence: 77%

Section: How Frequently Do Two White Dwarfs Merge?mentioning

confidence: 79%

Section: What Are the Origins Of High-mass White Dwarfs?mentioning

confidence: 99%

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Two delays in white dwarf evolution revealed byGaia

Cheng

2019

Proc. IAU

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“…Re-cent studies (Toonen et al 2017;Maoz et al 2018) suggest that binary mergers substantially contribute to the single WD population. The theoretical studies of Temmink et al (2020) estimated that 30-45% of the WDs more massive than 0.9M are formed through binary mergers, mostly via the merger of two WDs, and Cheng et al (2020) estimated observationally that the fraction of high-mass WDs (in the range of 0.8-1.3M ) that formed as a result of double WD mergers is nearly 20 %.…”

Section: Introductionmentioning

confidence: 99%

Forever young white dwarfs: When stellar ageing stops

Camisassa

Althaus

Torres

et al. 2021

A&A

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White dwarf stars are the most common end point of stellar evolution. The ultramassive white dwarfs are of special interest as they are related to type Ia supernovae explosions, merger events, and fast radio bursts. Ultramassive white dwarfs are expected to harbour oxygen-neon (ONe) cores as a result of single standard stellar evolution. However, a fraction of them could have carbon-oxygen (CO) cores. Recent studies, based on the new observations provided by the Gaia space mission, indicate that a small fraction of the ultramassive white dwarfs experience a strong delay in their cooling, which cannot be solely attributed to the occurrence of crystallisation, thus requiring an unknown energy source able to prolong their life for long periods of time. In this study, we find that the energy released by 22 Ne sedimentation in the deep interior of ultramassive white dwarfs with CO cores and high 22 Ne content is consistent with the long cooling delay of these stellar remnants. On the basis of a synthesis study of the white dwarf population, based on Monte Carlo techniques, we find that the observations revealed by Gaia can be explained by the existence of these prolonged youth ultramassive white dwarfs. Although such a high 22 Ne abundance is not consistent with the standard evolutionary channels, our results provide evidence for the existence of CO-core ultramassive white dwarfs and for the occurrence of 22 Ne sedimentation.

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“…Alternatively, mass transfer from the outer tertiary companion could drive the inner binary pair to merge or, more likely, collide with non-zero orbital eccentricity (e.g. Cheng et al 2020). Hydrodynamical simulations suggest that little mass ( 10 −3 M ) should be lost during the merger process, such that the final WD mass should be roughly equal to the sum of the masses of the progenitor WDs (Lorén-Aguilar et al 2009).…”

Section: Triples With Inner Binaries Containing Ms Stars And/or Wdsmentioning

confidence: 99%

Mergers of equal-mass binaries with compact object companions from mass transfer in triple star systems

Leigh

Toonen

Zwart

et al. 2020

Monthly Notices of the Royal Astronomical Society

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ABSTRACT In this paper, we consider triple systems composed of main-sequence (MS) stars, and their internal evolution due to stellar and binary evolution. Our focus is on triples that produce white dwarfs (WDs), where Roche lobe overflow of an evolving tertiary triggers accretion on to the inner binary via a circumbinary disc (CBD) driving it towards a mass ratio of unity. We present a combination of analytic- and population synthesis-based calculations performed using the SeBa code to constrain the expected frequency of such systems, given a realistic initial population of MS triples, and provide the predicted distributions of orbital periods. We identify the parameter space for triples that can accommodate a CBD, to inform future numerical simulations of suitable initial conditions. We find that ≳10 per cent of all MS triples should be able to accommodate a CBD around the inner binary, and compute lower limits for the production rates. This scenario broadly predicts mergers of near equal-mass binaries, producing blue stragglers (BSs), Type Ia supernovae, gamma-ray bursts and gravitational wave-induced mergers, along with the presence of an outer WD tertiary companion. We compare our predicted distributions to a sample of field BS binaries, and argue that our proposed mechanism explains the observed range of orbital periods. Finally, the mechanism considered here could produce hypervelocity MS stars, WDs, and even millisecond pulsars with masses close to the Chandrasekhar mass limit, and be used to constrain the maximum remnant masses at the time of any supernova explosion.

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Double White Dwarf Merger Products among High-mass White Dwarfs

Cited by 59 publications

References 80 publications

Two delays in white dwarf evolution revealed byGaia

Two delays in white dwarf evolution revealed byGaia

Forever young white dwarfs: When stellar ageing stops

Mergers of equal-mass binaries with compact object companions from mass transfer in triple star systems

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