Nuclear Reaction Rates in Highly Magnetized Relativistic Plasmas: Effects on Pulsational Pair-Instability Supernovae, Magnetar Nucleosynthesis, and Other Sites*

If an astrophysical environment is hot enough, screening in the associated nuclear reactions can be modified by the presence of a relativistic electron-positron plasma. Additionally, strong magnetic fields can create an additional enhancement as the electron and positron energy distribution is modified by the altered Landau level occupancy. This can result in a further enhancement of nuclear reaction rates, and the reaction rate enhancement factor is studied in several relevant scenarios. Nearly every astrophysical site may undergo shifts in nuclear reaction rates due to electron-positron screening at high temperatures and magnetic fields. Massive stars that undergo pulsational pair-instability can be affected by the relativistic plasma in the core, and results are presented including affects on the final black-hole mass, composition of matter ejected in the pulse, and stellar dynamical effects. In addition, results pertaining to r-process nucleosynthesis in collapsar and magnetar environments will be presented. In addition to relativistic thermal effects, strong magnetic fields can enhance weak rates, resulting in dramatically different r-process distributions. Effects on the the final r-process abundance and potential galactic chemical evolution results will be presented.