Carbon Shell or Core Ignitions in White Dwarfs Accreting From Helium Stars

Brooks, Jared; Bildsten, Lars; Schwab, Josiah; Paxton, Bill

doi:10.3847/0004-637x/821/1/28

Cited by 66 publications

(107 citation statements)

References 40 publications

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“…Due to this contraction at high central densities, thermal neutrino losses increase and degeneracy sets in, resulting in a degenerate core which is governed by the balance between heating due to contraction and cooling due to neutrino losses (Paczyński 1971;Nomoto 1984;Brooks et al 2016). In single stars, hydrogen and helium shell burning would cause the core to grow, and cooling as a result of neutrino losses would be offset by additional heating as a result of accretion due to core growth.…”

Section: Mass Loss After Core Carbon Burningmentioning

confidence: 99%

“…The expectation is that this model will continue to contract, reaching higher and higher densities, aided by the URCA process, eventually leading to conditions that are conducive for electron captures to occur. This path will depend on the core growth rate, as argued by Brooks et al (2016), and only detailed stellar models, which are able to avoid the discussed envelope instabilities, will provide us with clarity regarding this scenario.…”

Section: The Evolution Of the Cooling Core Towards Ecsnmentioning

confidence: 99%

“…Based on our models we see three possible scenarios, which all could be realized in various systems, depending on the initial conditions. The first possibility is based on scenario proposed by Paczyński (1971) and further developed by Schwab et al (2015); Brooks et al (2016). In this scenario, the ONe core continues to increases in density and electrons become increasingly degenerate.…”

Section: The Evolution Of the Cooling Core Towards Ecsnmentioning

confidence: 99%

“…As the density increases and the core temperature decreases, cooling due to plasma-neutrinos becomes less efficient, and eventually compressional heating slows down the cooling of the core. At some point in time, the neutrino cooling timescale, τ ν = c p T / ν , equals the compression timescale, τ comp = (d ln ρ/dt) −1 , and the evolution of the core will proceed along a trajectory which is primarily dependent on the core growth rate (Paczyński 1971;Brooks et al 2016). When high enough densities are reached, URCA processes will accelerate the contraction of the core toward densities where electron captures on 20 Ne and 24 Mg will induce core collapse.…”

Section: The Evolution Of the Cooling Core Towards Ecsnmentioning

confidence: 99%

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Electron Capture Supernovae from Close Binary Systems

Poelarends

Wurtz

Tarka

et al. 2017

ApJ

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We present the first detailed study of the Electron Capture Supernova Channel (ECSN Channel) for a primary star in a close binary star system. Progenitors of ECSN occupy the lower end of the mass spectrum of supernovae progenitors and are thought to form the transition between white dwarfs progenitors and core collapse progenitors . The mass range for ECSN from close binary systems is thought to be wider than the range for single stars, because of the effects of mass transfer on the helium core. Using the MESA stellar evolution code we explored the parameter space of initial primary masses between 8 M and 17 M , using a large grid of models . We find that the initial primary mass and the mass transfer evolution are important factors in the final fate of stars in this mass range. Mass transfer due to Roche Lobe overflow during and after carbon burning causes the core to cool down so that it avoids neon ignition, even in helium-free cores with masses up to 1.52 M , which in single stars would ignite neon. If the core is able to contract to high enough densities for electron captures to commence, we find that, for the adopted Ledoux convection criterion, the initial mass range for the primary to evolve into an ECSN is between 13.5 M and 17.6 M . The mass ratio, initial period, and mass loss efficiency only marginally affect the predicted ranges.

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Section: Mass Loss After Core Carbon Burningmentioning

confidence: 99%

Section: The Evolution Of the Cooling Core Towards Ecsnmentioning

confidence: 99%

Section: The Evolution Of the Cooling Core Towards Ecsnmentioning

confidence: 99%

Section: The Evolution Of the Cooling Core Towards Ecsnmentioning

confidence: 99%

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Electron Capture Supernovae from Close Binary Systems

Poelarends

Wurtz

Tarka

et al. 2017

ApJ

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“…In addition to this more detailed model of the standard He star + O/Ne WD chan-nel, we also speculate that He-star+C/O models that undergo carbon shell ignition before carbon core ignition can be a channel for AIC, as discussed in Brooks et al (2016). A core ignition of a C/O WD would lead to a SN Ia, but a shell ignition non-explosively transforms the C/O WD into an O/Ne WD, which continues to accrete until AIC is achieved.…”

Section: Introductionmentioning

confidence: 99%

Accretion-induced Collapse from Helium Star + White Dwarf Binaries

Brooks

Schwab

Bildsten

et al. 2017

ApJ

Self Cite

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Accretion-induced collapse (AIC) occurs when an O/Ne white dwarf (WD) grows to nearly the Chandrasekhar mass (M Ch ), reaching central densities that trigger electron captures in the core. Using Modules for Experiments in Stellar Astrophysics (MESA), we present the first true binary simulations of He star + O/Ne WD binaries, focusing on a 1.5M He star in a 3 hour orbital period with 1.1−1.3M O/Ne WDs. The helium star fills its Roche lobe after core helium burning is completed and donates helium on its thermal timescale to the WD,Ṁ ≈ 3 × 10 −6 M /yr, a rate high enough that the accreting helium burns stably on the WD. The accumulated carbon/oxygen ashes from the helium burning undergo an unstable shell flash that initiates an inwardly moving carbon burning flame. This flame is only quenched when it runs out of carbon at the surface of the original O/Ne core. Subsequent accumulation of fresh carbon/oxygen layers also undergo thermal instabilities, but no mass loss is triggered, allowing M WD → M Ch , triggering the onset of AIC. We also discuss the scenario of accreting C/O WDs that experience shell carbon ignitions to become O/Ne WDs, and then, under continuing mass transfer, lead to AIC. Studies of the AIC event rate using binary population synthesis should include all of these channels, especially this latter channel, which has been previously neglected but might dominate the rate.

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A helium-burning white dwarf binary as a supersoft X-ray source

Greiner

Maitra

Haberl

et al. 2023

Nature

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Type Ia supernovae are cosmic distance indicators1,2, and the main source of iron in the Universe3,4, but their formation paths are still debated. Several dozen supersoft X-ray sources, in which a white dwarf accretes hydrogen-rich matter from a non-degenerate donor star, have been observed5 and suggested as Type Ia supernovae progenitors6–9. However, observational evidence for hydrogen, which is expected to be stripped off the donor star during the supernova explosion10, is lacking. Helium-accreting white dwarfs, which would circumvent this problem, have been predicted for more than 30 years (refs. 7,11,12), including their appearance as supersoft X-ray sources, but have so far escaped detection. Here we report a supersoft X-ray source with an accretion disk whose optical spectrum is completely dominated by helium, suggesting that the donor star is hydrogen-free. We interpret the luminous and supersoft X-rays as resulting from helium burning near the surface of the accreting white dwarf. The properties of our system provide evidence for extended pathways towards Chandrasekhar-mass explosions based on helium accretion, in particular for stable burning in white dwarfs at lower accretion rates than expected so far. This may allow us to recover the population of the sub-energetic so-called Type Iax supernovae, up to 30% of all Type Ia supernovae13, within this scenario.

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Carbon Shell or Core Ignitions in White Dwarfs Accreting From Helium Stars

Cited by 66 publications

References 40 publications

Electron Capture Supernovae from Close Binary Systems

Electron Capture Supernovae from Close Binary Systems

Accretion-induced Collapse from Helium Star + White Dwarf Binaries

A helium-burning white dwarf binary as a supersoft X-ray source

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