text: The rapid proton capture process in X-ray bursts runs at the proton drip line except near some photodisintegration waiting points.  This includes the nuclei Mg, S, Ar, Ca, Ni, Zn, Ge, Se,
  Kr, Sr, and Zr.
  One clear nuclear structure pattern that emerges is the importance of pairing, as one notices all the waiting points above are at nuclei with an even number of protons, and all but Mg also have an even number of neutrons.  However, the waiting points will depend on the assumptions of the X-ray burst model, such as metallicity, accretion rate, and the hydrodynamics, along with the nuclear uncertainties, and as mentioned above, the exact definition of the waiting point may not be consistent from one study to the next. Although there are nuclear uncertainties, compared to other explosive nucleosynthesis processes, the rp-process is quite well experimentally constrained, as, for example, all the above waiting point nuclei have at the least been observed in the laboratory. Thus as the nuclear physics inputs can be found in the literature or data compilations, the [http://www.nucastrodata.org/infrastructure.html  Computational Infrastructure for Nuclear Astrophysics] allows one to do post-processing calculations on various X-ray burst models, and define for oneself the criteria for the waiting point, as well as alter any nuclear parameters.
  While the rp-process in X-ray bursts may have difficulty bypassing the Ge waiting point, certainly in X-ray pulsars where the rp-process is stable, instability toward alpha decay places an upper limit near A = 100 on the mass that can be reached through continuous burning. The exact limit is a matter presently under investigation; Te are known to undergo alpha decay whereas Sb is proton-unbound. Even before the limit near A = 100 is reached, the proton flux is thought to considerably decrease and thus slow down the rp-process, before low capture rate and a cycle of transmutations between isotopes of tin, antimony, and tellurium upon further proton capture terminate it altogether. However, it has been shown that if there are episodes of cooling or mixing of previous ashes into the burning zone, material as heavy as Xe can be created.