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Helium Flashes Through the NCO Reaction

Published online by Cambridge University Press:  12 April 2016

K. Arai
Affiliation:
Department of Physics, Kumamoto University, Kumamoto 860
K. Kaminisi
Affiliation:
Department of Physics, Kumamoto University, Kumamoto 860
M. Hashimoto
Affiliation:
Max Planck Institut für Astrophysik, Garching bei München D-8046
K. Nomoto
Affiliation:
Department of Earth Science and Astronomy, University of Tokyo Meguro-ku, Tokyo 153

Extract

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It is generally accepted that the helium flash occurs when the 3α reaction commences in the degenerate helium core of low mass stars. In this core, original CNO isotopes have been converted into 14N and the electron Fermi energy becomes large enough to approach the threshold energy for e-capture on 14N. Hence Kaminisi et al. (1975) have pointed out that in these circumstances the 14N(e, v)14C(α,γ)18O (NCO) reaction may play an important role for igniting the helium flash.

We, therefore, examine the effects of the NCO reaction on the evolution of low mass stars. A key ingredient of the NCO reaction is that the density reaches the threshold for e-capture (ρth≃ 106 g cm−3). Evolutionary sequences are presented for the cases of accreting helium white dwarfs (Hashimoto et al. 1986) and a 0.7 M, Population II star ascending the giant branch.

Type
Part I. Chemical Peculiarities as Probe of Stellar Evolution
Copyright
Copyright © Springer-Verlag 1988

References

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