Potential resonant screening effects on stellar 12C + 12C reaction rates

Cussons, R.; Langanke, K.; Liolios, Theodore E.

doi:10.1140/epja/i2002-10063-3

Cited by 15 publications

(29 citation statements)

References 7 publications

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“…Carbon burning proceeds mainly through 12 C( 12 C, α) 20 Ne and 12 C( 12 C, p) 23 Na reactions, the rates of which remain relatively uncertain, in particular because of the possible presence of low-energy resonances (Cussons et al 2003). This effect comes on top of the large uncertainties already affecting 12 C(α, γ) 16 O which primarily determines the carbon content inside the white dwarf.…”

Section: Effect Of Carbon Burning Rates Uncertaintiesmentioning

confidence: 99%

Evolution of massive AGB stars

Siess¹

2006

A&A

223

273

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We present new computations of the evolution of solar metallicity stars in the mass range 9−12 M . This first paper of a series focuses on the propagation of the carbon burning flame front and provides a detailed analysis of the structural evolution up to the formation of the neonoxygen core. Our calculations which do not include overshooting indicate that off-center carbon ignition is restricted to a small mass range between 9.0 and 11.3 M . The chemical imprints of the first and second dredge-ups on the surface composition are analyzed and compared to "standard" less massive stars. It results that, aside from being more luminous and slightly bluer in the HR diagram, massive AGB stars are almost indistinguishable from their lower mass counterparts, as far as the chemical composition is concerned. During the second dredge-up, we note however that the envelope penetrates deeper into the He burning shell than lower mass stars. Our simulations indicate that above ∼11.0 M , the depth of the second dredge up is considerably reduced, marking the transition between low and massive stars. We also investigate the effects of the nuclear uncertainties associated with 12 C + 12 C reactions and show that it has a little impact on the core composition. Finally we describe the nucleosynthesis and chemical structure of the newly formed neon-oxygen core.

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Section: Effect Of Carbon Burning Rates Uncertaintiesmentioning

confidence: 99%

Evolution of massive AGB stars

Siess¹

2006

A&A

223

273

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“…gives rise to further correction beside the screening and the potential resonant screening, already investigated in Cussons et al (2002); Itoh et al (2003). It is important to point out that the nonextensivity does not affect the other plasma corrections: therefore, we can define an effective factor F as…”

Section: Resonant Fusion Reactionsmentioning

confidence: 99%

“…By assuming the value of q = 0.991 of the entropic nonextensive parameters to evaluate nonextensive corrections we obtain that (i) the luminosity yield of the pp chain is slightly affected by the deformed statistics, with respect to the luminosity yield of the CNO cycle; (ii) the nonextensive CNO correction ranges from 37% to more than 53%; (iii) above T ≈ 2 × 10 7 K, the luminosity is mainly due to the CNO cycle only, thus confirming that CNO cycle always plays a crucial role in the stellar evolution, when the star grows hotter toward the white dwarf stage. Cussons et al (2002) proposed, on the basis of experimental measurements at energy E ∼ 2.4 MeV, that the resonant behavior of the stellar 12 C + 12 C fusion cross section could continue down to the astrophysical energy range, thus leading rise, beside the usual Debye-Hückel screening (whose corrective factor is f S ), to further plasma resonant screening effect (conventionally described by a suitable f RS factor). While f S > 1 enhances the reaction rate, it has been pointed out that f RS < 1, i.e.…”

Section: Resonant Fusion Reactionsmentioning

confidence: 99%

“…f T ≡ f S · f RS 1) because of the global screening domination that amounts to an enhancement of the rate by 12 orders of magnitude, with important implications for hydrostatic burning in carbon white dwarfs. Given the 12 C + 12 C reaction, the current hypothesis (Cussons et al, 2002) is that the entrance channel width is much smaller than the total resonance width, the latter being much smaller than the resonance energy. The same picture could possibly apply to other fusion reactions between medium-weighted nuclei (e.g.…”

Section: Resonant Fusion Reactionsmentioning

confidence: 99%

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Metastability of Electron-Nuclear Astrophysical Plasmas: Motivations, Signals and Conditions

Lavagno

Quarati

2006

Astrophys Space Sci

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Physical motivations indicating that the electronnuclear plasma of a stellar core (like the solar core) is not in a global thermodynamical equilibrium but satisfies the conditions of a metastable state are described. Momentum distributions of electrons and ions are nonextensive power law distributions, rather than the Maxwellian distribution of a global equilibrium state. Some open astrophysical problems are discussed as signals of deviations from global equilibrium description. The use of nonextensive distributions, appropriate in the case of metastable states, to evaluate atomic and nuclear rates of several processes in astrophysical systems, can lead to the solutions of the reported problems. Conditions of metastability for these systems are discussed.

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“…Cussons, Langanke and Liolios [28] proposed, on the basis of experimental measurements at energy E ∼ 2.4 MeV, that the resonant behavior of the stellar 12 C+ 12 C fusion cross section could continue down to the astrophysical energy range.…”

Section: Resonant Reaction Rates In Astrophysical Plasmamentioning

confidence: 99%

Quantum uncertainty in weakly non-ideal astrophysical plasma

Gervino¹,

Lavagno²,

Quarati³

2005

Braz. J. Phys.

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Galitskii and Yakimets showed that in dense or low temperature plasma, due to quantum uncertainty effect, the particle distribution function over momenta acquires a power-like tail even under conditions of thermodynamic equilibrium. We show that in weakly non-ideal plasmas, like the solar interior, both non-extensivity and quantum uncertainty should be taken into account to derive equilibrium ion distribution functions and to estimate nuclear reaction rates and solar neutrino fluxes. The order of magnitude of the deviation from the standard Maxwell-Boltzmann distribution can be derived microscopically by considering the presence of random electrical microfield in the stellar plasma. We show that such a nonextensive statistical effect can be very relevant in many nuclear astrophysical problems.

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Potential resonant screening effects on stellar 12C + 12C reaction rates

Cited by 15 publications

References 7 publications

Evolution of massive AGB stars

Evolution of massive AGB stars

Metastability of Electron-Nuclear Astrophysical Plasmas: Motivations, Signals and Conditions

Quantum uncertainty in weakly non-ideal astrophysical plasma

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