Gamma-ray Lines From cr Source Regions

Gamma-ray lines arise from radioactivities produced in nucleosynthesis sites, and from deexcitation of nuclei which have been activated through energetic particle collisions. Since the bulk of nucleosynthesis activity relates to activities inside massive stars, both these processes are related to the likely sources of cosmic rays: Supernova remnants show radioactivity afterglows at time scales which bracket their likely phases of relevance as CR acceleration sites; ²⁶Al radioactivity may trace regions of intense wind interactions from groups of massive stars, and also encode information about the possible injection of matter into CR acceleration environments through interstellar dust grains. The status of -ray line measurements after the Compton Observatory mission is presented, with models and interpretations of current results, and the prospects of upcoming measurements.