The Influence of¹⁴N(e⁻, ν)¹⁴C(α, γ)¹⁸O Reaction on He Ignition in Degenerate Physical Conditions

The importance of the 14 N( e - , γ) 14 C(α, γ) 18 O (NCO) chain to the onset of the He flash in degenerate physical conditions has been reevaluated. We find that low-mass, metal-rich ( Z ≥ 0.001) structures climbing the red giant branch never attain the physical conditions suitable for the onset of this chain, while at lower metallicities the energy contribution by the NCO reaction is too low to affect the onset of the central He flash. At the same time, our evolutionary models suggest that for a carbon-oxygen white dwarf of mass M WD = 0.6 M ☉ accreting He-rich matter at rates suitable for a dynamical He flash, directly or as a by-product of an overlying H-burning shell, the NCO energy contribution is not able to keep the He shell hot enough to avoid the occurrence of a strong electron degeneracy and the ensuing final explosion.