The $^{15}$O($alpha$,$gamma$)$^{19}$Ne Breakout Reaction and Impact on X-Ray Bursts

The breakout reaction $^{15}$O($alpha,gamma$)$^{19}$Ne, which regulates the flow between the hot CNO cycle and the rp-process, is critical for the explanation of the burst amplitude and periodicity of X-ray bursters. We report on the first successfulmeasurement of the critical $alpha$-decay branching ratios of relevant states in $^{19}$Ne populated via $^{19}$F($^3$He,t)$^{19}$Ne. Based on the experimental results and our previous lifetime measurements of these states, we derive the first experimental rate of $^{15}$O($alpha,gamma$)$^{19}$Ne. The impact of our experimental results on the burst pattern and periodicity for a range of accretion rates is analyzed.