Probing Cosmic Chemical Evolution with MeV Photons

Prof. Dieter H. Hartmann

Clemson University, Department of Physics and Astronomy

Multi-Messenger Astronomy recently opened the gravitational wave window. The detection of an electromagnetic MeV signal from a binary neutron star merger event (GW170817) with Fermi/GBM and INTEGRAL led to global follow-up observations revealing the expected kilonova emission powered by r-process nuclei produced in the merger. This allowed us to probe an exotic element synthesis processes, and high energy emission played a critical role in this breakthrough. The underexplored MeV window offers insights on a variety of additional astrophysical environments, including nuclear line emission from galactic supernova remnants and from nearby extragalactic supernovae (e.g., SNII 1987A and SNIa 2014J) and the diffuse galactic plane glow at 1.9 MeV from radioactive 26Al. The MeV band bridges the thermal and non-thermal universe, and we assess the value of observing in this challenging regime for understanding cosmic chemical evolution.