O 15 ( α , γ ) Ne 19 Breakout Reaction and Impact on X-Ray Bursts

The breakout reaction $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$, 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 successful measurement of the critical $\ensuremath{\alpha}$-decay branching ratios of relevant states in $^{19}\mathrm{Ne}$ populated via $^{19}\mathrm{F}(^{3}\mathrm{He},t)^{19}\mathrm{Ne}$. Based on the experimental results and our previous lifetime measurements of these states, we derive the first experimental rate of $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$. The impact of our experimental results on the burst pattern and periodicity for a range of accretion rates is analyzed.