Exploring the Carbon Simmering Phase: Reaction Rates, Mixing, and the Convective Urca Process

Schwab, Josiah; Martínez-Rodríguez, Héctor; Piro, Anthony L.; Badenes, Carles

doi:10.3847/1538-4357/aa9a3c

Cited by 18 publications

(13 citation statements)

References 69 publications

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“…In agreement with previous works [40][41][42][43][44] we obtain that electron captures and URCA pairs imply a net cooling of the inner region, C-ignition occurs at higher densities and both, the explosion density and the neutronization levels, are higher as compared with models that do not include URCA reactions.…”

Section: Models Results and Conclusionsupporting

confidence: 92%

Type Ia SN progenitors: pre-explosion phase in nearly Chandrasekhar mass WDs

et al. 2022

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Type Ia supernovae are used as distance indicators to measure the expansion rate of the Universe and to constrain the nature of dark energy. Current and upcoming surveys will allow to extend supernova Hubble diagrams to higher redshifts and to improve further their statistics. It is accepted that Type Ia supernovae are thermonuclear explosions of carbon-oxygen white dwarfs in binary systems. However, the identification of their progenitors, the evolutionary path leading to the explosion and the explosion mechanism itself have not been identified yet. This is critical, as we need to understand the potential evolution of their luminosity with cosmic time and, thus, with their stellar progenitors. We will review the current situation, considering observational hints. We will focus on our recent models, that follow the evolution of carbon-oxygen white dwarfs accreting mass up to thermonuclear runaway, and on their dependence with the initial metallicity of the white dwarf progenitors.

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Section: Models Results and Conclusionsupporting

confidence: 92%

Type Ia SN progenitors: pre-explosion phase in nearly Chandrasekhar mass WDs

et al. 2022

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“…The collapse-explosion puzzle of ECSNe cannot be solved solely from the theoretical side, due to the subtleties involved in simulations, such as the weak-reaction rates (Suzuki et al 2019;Strömberg et al 2021;Langanke et al 2021), convective URCA process (Paczyński 1973;Denissenkov et al 2015;Schwab et al 2017), convective mixing process driven by oxygen burning (Nomoto 1987;Zha et al 2019;Takahashi et al 2019), and physics of the oxygen flame (Leung et al 2020;Schwab et al 2020). Each scenario, i.e.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Simulations of Electron-capture Supernovae: Progenitor and Dimension Dependence

Zha,

O'Connor,

Couch

et al. 2021

Preprint

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We present neutrino-transport hydrodynamic simulations of electron-capture supernovae (ECSNe) in FLASH with new twodimensional (2D) collapsing progenitor models. These progenitor models feature the 2D modelling of oxygen-flame propagation until the onset of core collapse. We perform axisymmetric simulations with 6 progenitor models that, at the time of collapse, span a range of propagating flame front radii. For comparison, we also perform a simulation with the same setup using the canonical, spherically-symmetrical progenitor model n8.8. We found that the variations in the progenitor models inherited from simulations of stellar evolution and flame propagation do not significantly alter the global properties of the neutrino-driven ECSN explosion, such as the explosion energy (∼ 1.36-1.48 × 10 50 erg) and the mass (∼ 0.017-0.018𝑀 ) and composition of the ejecta. Due to aspherical perturbations induced by the 2D flame, the ejecta contains a small amount ( 1.8 × 10 −3 𝑀 ) of low-𝑌 𝑒 (0.35 < 𝑌 𝑒 < 0.4) component. The baryonic mass of the protoneutron star is ∼ 1.34 𝑀 (∼ 1.357 𝑀 ) with the new (n8.8) progenitor models when simulations end at ∼ 400 ms and the discrepancy is due to updated weak-interaction rates in the progenitor evolutionary simulations. Our results reflect the nature of ECSN progenitors containing a strongly degenerate ONeMg core and suggest a standardized ECSN explosion initialized by ONeMg core collapse. Moreover, we carry out a rudimentary three-dimensional simulation and find that the explosion properties are fairly compatible with the 2D counterpart. Our paper facilitates a more thorough understanding of ECSN explosions following the ONeMg core collapse, though more three-dimensional simulations are still needed.

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“…(see also Kushnir et al 2020), where we have used the solar Fe abundance X(Fe) = 1.292 × 10 In M Ch models this baseline Y e can in principle be reduced via weak reactions on carbon during the convective burning (or "simmering") phase prior to thermonuclear runaway (e.g., Piro & Bildsten 2008;Chamulak et al 2008;Schwab et al 2017), although Martínez-Rodríguez et al (2016) show the impact to be negligible (reduction in Y e of 10 −4 only; but see Piersanti et al 2017 for a different view). However, the higher densities of M Ch WDs (up to 2−3 × 10 9 g cm −3 ; see Fig.…”

Section: Nuclear Statistical Equilibriummentioning

confidence: 99%

Stable nickel production in Type Ia supernovae: A smoking gun for the progenitor mass?

Blondin,

Bravo,

Timmes

et al. 2021

Preprint

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Context. There are now strong indications that white dwarf (WD) stars with masses well below the Chandrasekhar limit (M Ch ≈ 1.4 M ) contribute a significant fraction of SN Ia progenitors. The relative fraction of stable iron-group elements synthesized in the explosion has been suggested as a possible discriminant between M Ch and sub-M Ch events. In particular, it is thought that the higherdensity ejecta of M Ch WDs, which favours the synthesis of stable isotopes of nickel, results in prominent [Ni ii] lines in late-time spectra ( 150 d past explosion). Aims. We study the explosive nucleosynthesis of stable nickel in SNe Ia resulting from M Ch and sub-M Ch progenitors, and explore the potential for lines of [Ni ii] in the optical an near-infrared (at 7378 Å and 1.94 µm) in late-time spectra to serve as a diagnostic of the exploding WD mass. Methods. We review stable Ni yields in a large variety of published SN Ia models. Using 1D M Ch delayed-detonation and sub-M Ch detonation models, we study the synthesis of stable Ni isotopes (in particular 58 Ni), and investigate the formation of [Ni ii] lines using nonlocal thermodynamic equilibrium radiative-transfer simulations with the CMFGEN code. Results. We confirm that stable Ni production is in general more efficient in M Ch explosions at solar metallicity (typically 0.02-0.08 M for the 58 Ni isotope), but note that the 58 Ni yields in sub-M Ch events systematically exceed 0.01 M for WDs more massive than one solar mass. We find that the radiative proton-capture reaction 57 Co(p, γ) 58 Ni is the dominant production mode for 58 Ni in both M Ch and sub-M Ch models, while the α-capture reaction on 54 Fe has a negligible impact on the final 58 Ni yield. More importantly, we demonstrate that the lack of [Ni ii] lines in late-time spectra of sub-M Ch events is not always due to an under-abundance of stable Ni, but results from the higher ionization of Ni in the inner ejecta. Conversely, the strong [Ni ii] lines predicted in our 1D M Ch models are completely suppressed when 56 Ni is sufficiently mixed with the innermost layers rich in stable iron-group elements. Conclusions. [Ni ii] lines in late-time SN Ia spectra have a complex dependency on the abundance of stable Ni, which limits their use alone in distinguishing between M Ch and sub-M Ch progenitors. However, we argue that a low-luminosity SN Ia displaying strong [Ni ii] lines would most likely result from a Chandrasekhar-mass progenitor.

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Exploring the Carbon Simmering Phase: Reaction Rates, Mixing, and the Convective Urca Process

Cited by 18 publications

References 69 publications

Type Ia SN progenitors: pre-explosion phase in nearly Chandrasekhar mass WDs

Type Ia SN progenitors: pre-explosion phase in nearly Chandrasekhar mass WDs

Hydrodynamic Simulations of Electron-capture Supernovae: Progenitor and Dimension Dependence

Stable nickel production in Type Ia supernovae: A smoking gun for the progenitor mass?

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