Mixing via Thermocompositional Convection in Hybrid C/O/Ne White Dwarfs

Schwab, Josiah; Garaud, Pascale

doi:10.3847/1538-4357/ab113f

Cited by 10 publications

(9 citation statements)

References 41 publications

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“…Model A is a scenario where a hybrid CONe WD arrives near the Chandrasekhar mass by accretion, when an off-centre deflagration burns only in the carbon-rich material, with the explosion ejecting mass to look like a low-luminosity SN, while leaving behind a remnant WD (Kromer et al 2015). (This Model A has substantial problems with the convective mixing, both at the time of formation and during an interval of simmering before ignition, such that the hybrid 2-layer structure is unlikely, with Model A then not making even a weak SN explosion, see Lecoanet et al 2016 andGaraud 2019. ) This is essentially a single-degenerate Type Ia supernova that has failed to burn much of the WD because much of mass is of ONe composition.…”

Section: Model A; Explosion Of Hybrid Cone White Dwarfmentioning

confidence: 99%

The Path from the Chinese and Japanese Observations of Supernova 1181 AD, to a Type Iax Supernova, to the Merger of CO and ONe White Dwarfs

Schaefer¹

2023

Preprint

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In 1181 AD, Chinese and Japanese observers reported a bright 'Guest Star' in the constellation Chuanshe, unmoving and visible for 185 days. In 2013, D. Patchick discovered a unique nebula surrounding a unique star, with two groups attributing this structure, named 'Pa 30', to be the supernova remnant of SN 1181, as a sub-subclass of supernova, the low-luminosity Type Iax. Here, I provide a wide range of new observational evidence: First, a detailed analysis of the original Chinese and Japanese reports places the 'Guest Star' of 1181 into a small region with the only interesting source being Pa 30. Second, the ancient records confidently place the peak magnitude as 0.0>𝑉 peak >−1.4, and hence peak absolute magnitude of −14.5>𝑀 V,peak >−16.0 mag. Third, the Pa 30 central star is fading from 𝐵=14.90 in 1917, to 𝐵=16.20 in 1950, to 𝐵=16.58 in 2022. Fourth, recent light curves show typical variability with full-amplitude of 0.24 mag on time-scales of one day and longer, critically with no coherent modulations for periods from 0.00046-10 days to strict limits. Fifth, the spectral energy distribution from the far-infrared to the ultraviolet is a nearly perfect power-law with 𝐹 𝜈 ∝ 𝜈 0.99±0.07 , observed luminosity of 128±24 L , and absolute magnitude 𝑀 V =+1.07. I collect my new evidences with literature results to make a confident case to connect the Oriental observations to a supernova, then to Pa 30, then to a low-luminosity Type Iax SN, then to the only possible explosion mechanism as a merger between CO and ONe white dwarfs.

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Section: Model A; Explosion Of Hybrid Cone White Dwarfmentioning

confidence: 99%

The Path from the Chinese and Japanese Observations of Supernova 1181 AD, to a Type Iax Supernova, to the Merger of CO and ONe White Dwarfs

Schaefer¹

2023

Preprint

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“…For the dimensionless numbers above, we use Ra T = 1.5 × 10 5 , Le = 3.3, Pr = 0.5, and Sc = 1.6. We selected Pr and Le slightly below and above unity, respectively, and a moderate value of Ra T , to be in the astrophysical regime (Pr = 1, 1 = Le = Ra T , e.g., Schwab & Garaud 2019;Garaud 2021b) and remain in a numerically tractable region of the parameter space. The strength of the convective flow is controlled by changing the flux of light elements at the boundaries.…”

Section: Model and Simulation Setupmentioning

confidence: 99%

Heat Transport and Convective Velocities in Compositionally Driven Convection in Neutron Star and White Dwarf Interiors

Fuentes

Cumming

Castro-Tapia

et al. 2023

ApJ

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We investigate heat transport associated with compositionally driven convection driven by crystallization at the ocean–crust interface in accreting neutron stars, or growth of the solid core in cooling white dwarfs. We study the effect of thermal diffusion and rapid rotation on the convective heat transport, using both mixing length theory and numerical simulations of Boussinesq convection. We determine the heat flux, composition gradient, and Péclet number, Pe (the ratio of thermal diffusion time to convective turnover time) as a function of the composition flux. We find two regimes of convection with a rapid transition between them as the composition flux increases. At small Pe, the ratio between the heat flux and composition flux is independent of Pe, because the loss of heat from convecting fluid elements due to thermal diffusion is offset by the smaller composition gradient needed to overcome the reduced thermal buoyancy. At large Pe, the temperature gradient approaches the adiabatic gradient, saturating the heat flux. We discuss the implications for cooling of neutron stars and white dwarfs. Convection in neutron stars spans both regimes. We find rapid mixing of neutron star oceans, with a convective turnover time of the order of weeks to minutes depending on rotation. Except during the early stages of core crystallization, white dwarf convection is in the thermal-diffusion-dominated fingering regime. We find convective velocities much smaller than recent estimates for crystallization-driven dynamos. The small fraction of energy carried as kinetic energy calls into question the effectiveness of crystallization-driven dynamos as an explanation for observed magnetic fields in white dwarfs.

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“…With a remnant lifetime of ∼ 100 kyr, this would predict as many as ∼ 100 galactic objects currently in this phase. ing, convection and thermohaline mixing driven by the electron fraction gradient can redistribute this neutronrich material deeper into the interior (e.g., Brooks et al 2017;Schwab & Garaud 2019).…”

Section: Post-merger To Wd Cooling Trackmentioning

confidence: 99%

The final fates of close hot subdwarf - white dwarf binaries: mergers involving He/C/O white dwarfs and the formation of unusual giant stars with C/O-dominated envelopes

Schwab,

Bauer

2021

Preprint

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Recently, a class of Roche-lobe-filling binary systems consisting of hot subdwarf stars and white dwarfs with sub-hour periods has been discovered. At present, the hot subdwarf is in a shell He burning phase and is transferring some of its remaining thin H envelope to its white dwarf companion. As the evolution of the hot subdwarf continues, it is expected to detach, leaving behind a low mass C/O core WD secondary with a thick He layer. Then, on a timescale of ∼ 10 Myr, gravitational wave radiation will again bring the systems into contact. If the mass transfer is unstable and results in a merger and a catastrophic thermonuclear explosion is not triggered, it creates a remnant with a C/O-dominated envelope, but one still rich enough in He to support an R Corona Borealis-like shell burning phase. We present evolutionary calculations of this phase and discuss its potential impact on the cooling of the remnant WD.

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Mixing via Thermocompositional Convection in Hybrid C/O/Ne White Dwarfs

Cited by 10 publications

References 41 publications

The Path from the Chinese and Japanese Observations of Supernova 1181 AD, to a Type Iax Supernova, to the Merger of CO and ONe White Dwarfs

The Path from the Chinese and Japanese Observations of Supernova 1181 AD, to a Type Iax Supernova, to the Merger of CO and ONe White Dwarfs

Heat Transport and Convective Velocities in Compositionally Driven Convection in Neutron Star and White Dwarf Interiors

The final fates of close hot subdwarf - white dwarf binaries: mergers involving He/C/O white dwarfs and the formation of unusual giant stars with C/O-dominated envelopes

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