Nuclear reaction rates in dense carbon-oxygen mixtures

Ogata, Shūji; Iyetomi, Hiroshi; Ichimaru, Setsuo

doi:10.1086/169971

Cited by 64 publications

(69 citation statements)

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“…Our simulations are 10 to 20 times longer than those given by Ogata et al 8 , and consequently our MC error, i.e. noise, is roughly ± 0.0001 to ± 0.0007.…”

Section: Helmholtz Free Energymentioning

confidence: 40%

“…4 and 5, the earlier work of Ogata et al 8 , and the recent direct MC sampling of Ogata 9 . The direct Monte Carlo sampling method of Ogata 10 agrees with our results to within about 1%.…”

Section: Widom Expansionmentioning

confidence: 78%

“…ii) Fitting the available MC data points to the Widom expansion which gives H(x) in powers 6 of x 2 . Both approaches were used by Rosenfeld 7 and found to give comparable accuracy using the data given by Ogata et al 8 . Recently Ogata 9 has presented a direct Monte Carlo sampling method to obtain H(0).…”

Section: Introductionmentioning

confidence: 97%

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Screening Enhancement of Thermonuclear Reactions in High Density Stars

DeWitt

Slattery

1999

Contrib. Plasma Phys.

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September 28, 1998This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author. PREPRINT ABSTRACTThe screening function for zero separation for two is reacting nuclei in a strongly coupled OCP plasma is obtained using new very accurate Monte Carlo OCP fluid simulation data by two methods. The first method obtains, H(0), the screening function at x =0, from the difference of free energies before and after the reaction.The second method is a direct fitting of the Widom expansion in powers of x 2 to the MC data for the pair distribution function, g(x). The two methods agree to .2%. INTRODUCTIONThermonuclear reaction rates in high density stars, such as the onset of C -C reactions in white dwarf stars, are governed by the probability that the two reacting nuclei get sufficiently close that they can tunnel through the Coulomb barrier. Screening by neighboring ions significantly reduces this barrier. The dominant effect in the fluid portion of the white dwarfs is governed by the screening function defined by the ion-ion pair distribution function:

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“…Our simulations are 10 to 20 times longer than those given by Ogata et al 8 , and consequently our MC error, i.e. noise, is roughly ± 0.0001 to ± 0.0007.…”

Section: Helmholtz Free Energymentioning

confidence: 40%

“…4 and 5, the earlier work of Ogata et al 8 , and the recent direct MC sampling of Ogata 9 . The direct Monte Carlo sampling method of Ogata 10 agrees with our results to within about 1%.…”

Section: Widom Expansionmentioning

confidence: 78%

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Screening Enhancement of Thermonuclear Reactions in High Density Stars

DeWitt

Slattery

1999

Contrib. Plasma Phys.

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“…The radiative opacities from OPAL (Iglesias & Rogers 1996) and the conductivities of Itoh et al (1983) were used. Nuclear reaction rates and energies are from Caughlan & Fowler (1988), with screening enhancement factors for high density from Ichimaru (1993), which also appear in Ogata, Iyetomi, & Ichimaru (1991).…”

Section: Accreting Envelopementioning

confidence: 99%

Theoretical Modeling of the Thermal State of Accreting White Dwarfs Undergoing Classical Nova Cycles

Townsley

Bildsten

2004

ApJ

144

156

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White dwarfs (WDs) experience a thermal renaissance when they receive mass from a stellar companion in a binary. For accretion rates of less than 10 À8 M yr À1 , the freshly accumulated hydrogen/helium envelope ignites in a thermally unstable manner that results in a classical nova (CN) outburst and ejection of material. We have undertaken a theoretical study of the impact of the accumulating envelope on the thermal state of the underlying WD. This has allowed us to find the equilibrium WD core temperatures (T c ), the CN ignition masses (M ign ), and the thermal luminosities for WDs accreting at rates of 10 À11 to 10 À8 M yr À1 . These accretion rates are most appropriate for WDs in cataclysmic variables (CVs) of P orb P 7 hr, many of which accrete sporadically as dwarf novae. We have included 3 He in the accreted material at levels appropriate for CVs and find that it significantly modifies the CN ignition mass. We compare our results with several others from the CN literature and find that the inclusion of 3 He leads to lower values of M ign for hM _ i k 10 À10 M yr À1 and that for hM _ i values below this the particular author's assumption concerning T c , which we calculate consistently, is a determining factor. Initial comparisons of our CN ignition masses with measured ejected masses find reasonable agreement and point to ejection of material comparable to that accreted.

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“…While Monte Carlo calculations have now developed to the point where relatively accurate values can be obtained for the screening potential when two reacting nuclei are separated by distances comparable to the average distance between nuclei in the plasma, the extrapolation of these results to near-zero separation, where the nuclear reaction occurs, has recently become the subject of some controversy. Ogata, Iyetomi, and Ichimaru (1991) have employed their most recent, highly accurate Monte Carlo results, extrapolated to zero separation by a technique they developed, to obtain a parametrized form for the screened C+C thermonuclear reaction rate both in the high-density fluid phase and in the solid phase of a C / 0 plasma. This is the first detailed calculation of the enhancement factor for nuclear reaction rates for a binary ionic mixture (BIM).…”

Section: I4i C-ignitionmentioning

confidence: 99%

Equations of State in Stellar Structure and Evolution

Horn

1994

International Astronomical Union Colloquium

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In this paper I summarize some of the recent advances in studies of dense matter. Research on phase separation in the binary ionic mixtures (BIMs) that constitute the matter in white dwarfs has been motivated by the need to obtain accurate estimates for the ages of the faintest white dwarfs and thus of the disk of our Galaxy. Substantial age increases appear possible, but it is not yet clear whether such large increases occur in real white dwarfs. A second advance is the prediction, based on state-of-the-art physical calculations, that ionization of H at low temperatures and increasing densities may occur via a first-order "plasma phase transition" (PPT). Astrophysical consequences of this result are still being explored in an effort to test this prediction. Related to these equation-of-state calculations are calculations of the enhancement of nuclear reaction rates at high densities. New thermonuclear rates have been computed for C+C reactions in BIMs, although there is currently some controversy about results at the highest densities. New pycnonuclear reaction rates have also been calculated for BIMs, and it has been suggested that He-burning at T = 0 may occur through a first-order phase transition. Finally, calculations of the equation of state of matter in strong magnetic fields and of radiative opacities at high densities have undergone very recent and substantial improvements, which are just beginning to be utilized in astrophysical calculations.Dans cette revue, je resumme les travaux les plus recents dans l'etude

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Nuclear reaction rates in dense carbon-oxygen mixtures

Cited by 64 publications

References 0 publications

Screening Enhancement of Thermonuclear Reactions in High Density Stars

Screening Enhancement of Thermonuclear Reactions in High Density Stars

Theoretical Modeling of the Thermal State of Accreting White Dwarfs Undergoing Classical Nova Cycles

Equations of State in Stellar Structure and Evolution

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