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The evolving optical and infrared kilonova was consistent with radioactive heating of neutron-rich merger ejecta. Rapid neutron capture, the r-process, can synthesize nuclei heavier than iron; decay of the newly formed unstable nuclei powers the transient. Its redward evolution and large inferred opacity supported production of heavy-element-rich ejecta. Thus mergers are a demonstrated important site for heavy-element production, while the fractions of individual elements and their total cosmic contribution remain model-dependent. The transient was not a direct identification of every very heavy element.^[ref]

The short gamma-ray burst GRB 170817A followed the merger signal by about $1.7\mathrm{s}$, providing direct evidence that at least some short gamma-ray bursts arise from neutron star mergers. The association connects their high-energy emission and relativistic outflows to compact-binary coalescence. It does not establish that every short burst has this progenitor, nor that the observed gamma-ray luminosity is independent of viewing angle.^[ref]