CNO cycle

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CNO cycle
Energetics Q Q4p?4He En 26.73 MeV 0.706
MeV 0.996 MeV 25.028 MeV
13N(b)
15O(b)
All initial abundances within a cycle serve as
catalysts and accumulate at largest t
Extended cycles introduce outside material into
CN cycle (Oxygen,
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ColdCNO cycle
Hot CNO cycle
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CNO cycle abundance evolution into steady state
(from Iliadis)
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Competition between the p-pchain and the CNO
Cycle
The main reason are different slopes due to
different temperaturedependencies of pp and
14N(p,g)
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Competition between the p-pchain and the CNO
Cycle
But exact cross over also depends on other
variables

• So in addition to the reaction rates the ratio
  depends on
• initial CN abundance YCNinitial
• current H abundance Yp
• different neutrino loss fractions

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