High-precision mass measurement of ${}^{24}$Si and a refined determination of the $rp$ process at the $A=22$ waiting point

We report a high precision mass measurement of ${}^{24}\mathrm{S}\mathrm{i}$, performed with the LEBIT facility at the National Superconducting Cyclotron Laboratory. The atomic mass excess, $10753.8$(37) keV, is a factor of 5 more precise than previous results. This substantially reduces the uncertainty of the ${}^{23}\mathrm{A}\mathrm{l}(p,\gamma {)}^{24}\mathrm{S}\mathrm{i}$ reaction rate, which is a key part of the rapid proton capture ($rp$) process powering Type I X-ray bursts. The updated rate constrains the onset temperature of the $(\alpha ,p)$ process at the ${}^{22}\mathrm{M}\mathrm{g}$ waiting-point to a precision of 9%.