The ring-shaped shadow of rotating naked singularity with a complete photon sphere

Understand

We investigate the shadows of Konoplya-Zhidenko naked singularity.

• In the spacetime of Konoplya-Zhidenko naked singularity, not only can unstable retrograde light ring (LR) exist, but also unstable prograde LR, leading to the formation of a complete photon sphere (PS).
• Due to the absence of an event horizon, a dark disc-shaped shadow does not appear; instead, a ring-shaped shadow is observed.
• The ring-shaped shadow appears as an infinite number of relativistic Einstein rings in the image of the naked singularity.