Heavy Elements and Electromagnetic Transients from Neutron Star Mergers

Compact binary mergers involving neutron stars can eject a fraction of their mass to space. Being extremely rich, this material undergoes rapid capture nucleosynthesis, and the resulting radioactivity powers fast, short-lived electromagnetic transients known as kilonova or macronova. Such are exciting probes most extreme physical conditions observation signals enrichment Universe with heavy elements. Here current understanding ejection mechanisms, properties ejecta, radioactive reviewed. The first well-observed event in aftermath GW170817 delivered wealth insights, but much today's picture such events is still based on patchwork theoretical studies. Apart from summarizing understanding, questions where no consensus has been reached yet also pointed out, possible directions for future research sketched. In an appendix, publicly available heating rate library WinNet nuclear reaction network described, simple fit formula alleviate implementation hydrodynamic simulations provided.