Photon structure of stationary spaces

This work is devoted to the analysis of photon surfaces and photon regions in the stationary Plebański–Demiański space–time, including black holes, naked singularities, and wormholes, with rotation, the electric or magnetic charge, the NUT parameter, the acceleration parameter, and the cosmological constant taken into account. We construct a theory of partially umbilic hypersurfaces, which allows us to describe the photon structure of space–time without resorting to the analysis of geodesic equations. We completely classify photon surfaces for various values of the parameters, including critical ones at which a qualitative change in the photon structure occurs. The results are visualized in the form of diagrams, which allows compactly presenting the information needed to understand strong gravitational lensing and gravitational shadows.