The Final Evolution of ONeMg Electron-Degenerate Cores

Gutiérrez, Javier Franch; Garcı́a–Berro, E.; Iben, Icko; Isern, J.; Labay, J.; Canal, R.

doi:10.1086/176934

Cited by 102 publications

(111 citation statements)

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“…On the contrary, if NSE was reached at densities below this critical density, the degenerate object would be completely disrupted. Finally, Gutiérrez et al (1996) analyzed the role of Coulomb corrections, both in the equation of state and in the electron-capture threshold energies, and found that explosive NeO ignition takes place at densities high enough to ensure gravitational collapse to nuclear matter densities. The previously described scenario should apply not only to the cores of Super-Asymptotic Giant Branch (SAGB) stars (García-Berro & Iben 1994) but also to ONeMg white dwarfs accreting material from a companion in a close binary system (Miyaji et al 1980;Nomoto 1984Nomoto , 1987.…”

Section: Introductionmentioning

confidence: 99%

The gravitational collapse of ONe electron-degenerate cores and white dwarfs: The role of $^\mathsf{24}$Mg and $^\mathsf{12}$C revisited

Gutiérrez¹,

Canal

Garcı́a–Berro

2005

A&A

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Abstract. The final stages of the evolution of electron-degenerate ONe cores, resulting from carbon burning in "heavy weight" intermediate-mass stars (8 M < ∼ M < ∼ 11 M ) and growing in mass, either from carbon burning in a shell or from accretion of matter in a close binary system, are examined in the light of their detailed chemical composition. In particular, we have modelled the evolution taking into account the abundances of the following minor nuclear species, which result from the previous evolutionary history: 12 C, 23 Na, 24 Mg, and 25 Mg. Both 23 Na and 25 Mg give rise to Urca processes, which are found to be unimportant for the final outcome of the evolution. 24 Mg was formerly considered a major component of ONe cores (hence called ONeMg cores), but updated evolutionary calculations in this mass range have severely reduced its abundance. Nevertheless, we have parameterized it and we have found that the minimum amount of 24 Mg required to produce NeO burning at moderate densities is ∼23%, a value exceedingly high in the light of recent evolutionary models. Finally, we have determined that models with relatively small abundances of unburnt carbon (X( 12 C) ∼ 0.015) could be a channel to explosion at low to moderate density (∼1 × 10 9 g cm −3 ). This is clearly below the current estimate for the explosion/collapse threshold and would have interesting consequences.

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Section: Introductionmentioning

confidence: 99%

The gravitational collapse of ONe electron-degenerate cores and white dwarfs: The role of $^\mathsf{24}$Mg and $^\mathsf{12}$C revisited

Gutiérrez¹,

Canal

Garcı́a–Berro

2005

A&A

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“…In this case the white dwarf can accrete mass from the secondary and the central density can eventually become larger than the threshold for electron captures on the ashes of carbon burning, as occurs for single stars with masses larger than ∼10.5 M . As previously mentioned, in both cases the final evolution depends sensitively on the final abundances of 12 C, 16 O, 20 Ne, and 24 Mg, and the final outcome (explosion or collapse) is crucially dependent on the adopted prescription for convective mixing (Gutiérrez et al 1996(Gutiérrez et al , 2005. In any case, it is clear that at least some of these stars will produce produce massive ONe white dwarfs.…”

Section: Possible Outcomes Of Sagb Starsmentioning

confidence: 90%

“…This has implications for accretion induced collapse, in the event that a white dwarf or a degenerate core of a SAGB star of initially ∼1.1 M can grow in mass to reach the effective Chandrasekhar limit of ∼1.37 M (Miyaji & Nomoto 1987). In such a case carbon will ignite before oxygen does and the energy released by the burning of even small amounts of carbon (∼2%) is sufficent to completely disrupt the star (Gutiérrez et al 1996;Gutiérrez et al 2005). Note also the absence of 22 Ne in the very outer layers of the carbon-rich degenerate core, where this element has been converted to 25 Mg. On top of these regions a helium-rich buffer exists (not shown).…”

Section: Overview Of the Carbon-burning Phasementioning

confidence: 99%

The Formation and Evolution of ONe White Dwarfs: Prospects for Accretion Induced Collapse

Garcı́a–Berro

2011

Proc. IAU

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Abstract. I review our current understanding of the evolution of stars which experience carbon burning under conditions of partial electron degeneracy and ultimately become thermally pulsing "super" asymptotic giant branch (SAGB) stars with electron-degenerate cores composed primarily of oxygen and neon. The range in stellar mass over which this occurs is very narrow and the interior evolutionary characteristics vary rapidly over this range. Consequently, while those stars with larger masses (∼11 M ) are likely to undergo electron-capture accretion induced collapse, those models with smaller masses (8.5 < ∼ M/M < ∼ 10.5) will presumably form massive (M > ∼ 1.1 M ) white dwarfs. The final outcome depends sensitively on the adopted mass-loss rates, the chemical composition of the massive envelopes, and on the adopted prescription for convective mixing.

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“…For this reason it is crucial to include Coulomb corrections to the electron chemical potential, µ e , and to the rate, both of which raise the effective threshold density (Gutierrez et al 1996).…”

Section: Preliminary Modelsmentioning

confidence: 99%

Progenitors of electron-capture supernovae

Jones

Hirschi

Herwig³

et al. 2011

Proc. IAU

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Abstract. We investigate the lowest mass stars that produce Type-II supernovae, motivated by recent results showing that a large fraction of type-II supernova progenitors for which there are direct detections display unexpectedly low luminosity (for a review see e.g. Smartt 2009). There are three potential evolutionary channels leading to this fate. Alongside the standard 'massive star' Fe-core collapse scenario we investigate the likelihood of electron capture supernovae (ECSNe) from super-AGB (S-AGB) stars in their thermal pulse phase, from failed massive stars for which neon burning and other advanced burning stages fail to prevent the star from contracting to the critical densities required to initiate rapid electron-capture reactions and thus the star's collapse. We find it indeed possible that both of these relatively exotic evolutionary channels may be realised but it is currently unclear for what proportion of stars. Ultimately, the supernova light curves, explosion energies, remnant properties (see e.g. Knigge et al. 2011) and ejecta composition are the quantities desired to establish the role that these stars at the lower edge of the massive star mass range play.Keywords. stars: evolution, supernovae: general Preliminary modelsFor stars that develop degenerate ONe cores with M ONe 1.37M , neon is ignited off-centre. Such an ignition was also found in the models of Nomoto (1984), but the subsequent evolution was not followed to a conclusion. As we discuss below, the nucleosynthesis in these neon-burning shells becomes rather complex and the speed and nature of their inward propagation determine the evolutionary outcome.We computed a 9M model from pre-main sequence using the MESA code (Paxton et al. 2011). Following the main sequence and core He-burning, our model ignites carbon non-degenerately at its centre where the stellar material becomes convectively unstable, which is typical of a massive star with M ini /M 20. Following the ignition of convective secondary carbon burning shells, neon is ignited at the co-ordinate ∼ 0.75M away from the centre. Ignition takes place where the maximum temperature now resides due to a temperature inversion in the core caused by the onset of degeneracy following the central extinction of carbon.The centre contracts since there is no constant source of energy production there, only neutrino losses and URCA cooling. Meanwhile, energy production in the shell pushes the temperature there high enough to ignite oxygen, leaving behind mostly isotopes of Si and S. We find that the shell propagates by means of compressional heating, when 341 at https://www.cambridge.org/core/terms. https://doi

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The Final Evolution of ONeMg Electron-Degenerate Cores

Cited by 102 publications

References 0 publications

The gravitational collapse of ONe electron-degenerate cores and white dwarfs: The role of $^\mathsf{24}$Mg and $^\mathsf{12}$C revisited

The gravitational collapse of ONe electron-degenerate cores and white dwarfs: The role of $^\mathsf{24}$Mg and $^\mathsf{12}$C revisited

The Formation and Evolution of ONe White Dwarfs: Prospects for Accretion Induced Collapse

Progenitors of electron-capture supernovae

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