Speaker
Description
I will briefly review key observational evidence constraining the sources and properties of UHECRs, and show that it points to BNS mergers as the source. The main topic of the talk is predicting the spectrum and composition of UHECRs in the BNS merger scenario, which is possible to do in unprecedented specificity thanks to the source-to-source similarity of the ejecta. I use the high-resolution neutrino-GRMHD simulation of Kiuchi et al (2023) to initialize the B field, then follow its expansion. The highest rigidity UHECRs (R==E/Z) are produced where magnetic acceleration out-competes synchrotron loss; this enables prediction of the peak energy for each nucleus (Z,A), in good agreement with data. I note a possible secondary, higher energy p or He contribution from jet acceleration and discuss how nuclear physics will play a critical role in predicting the relative contributions of different nuclei to the spectrum. Muiltimessenger consequences will be discussed.
