Hydrogen burning of O in the CNO cycle

The direct capture process in the ¹⁷O(p, γ)¹⁸F reaction has been used to determine the reduced proton widths of the states in ¹⁸F near the proton threshold. The observed upper limits on these widths are up to factors of 60 smaller than the previously assumed values implying a corresponding reduction of the stellar reaction rate for the ¹⁷O(p, )¹⁴N reaction. These results together with results from previous work lead to the conclusion that the CNO cycle is tricycling with the reactions ¹⁷O(p,γ)¹⁸F(β⁺ν)¹⁸O(p, )¹⁵N as the third cycle. The implications of these results on the equilibrium abundances of the elements synthesized in this cycle are discussed.