Electromagnetic Probes of the Supernova Engine

Explosions from stellar collapse are important in nearly all aspects of astronomy: formation of compact remnants (including the potential seeds of supermassive black holes), the production of compact binaries the produce X-ray binaries and radio pulsars, the origin of many of the heavy elements (a critical aspect of galactic chemical evolution), and as standard candles to probe the early universe (including the nature of star formation). Because these explosions occur in extreme conditions, if we can understand them, they can be used to probe fundamental physics: matter at extreme densities (exceeding nuclear densities, quark formation), neutrino physics (including neutrino oscillations) and, in black-hole forming systems, the nature of relativity. Gravitational waves and neutrinos provide the most direct probe of stellar collapse, but these diagnostics require nearby events. Electromagnetic probes, from shock breakout to observations of supernova remnants, can be much more common and provide complementary diagnostics of the explosive engines behind stellar collapse. In this review, we review these electromagnetic diagnostics, the physics behind them and the theory and modeling work we require to take advantage of these probes.