Charged black-bounce spacetimes: Photon rings, shadows and observational appearances

The photon ring, shadow and observational appearance of the emission originating near a charged black-bounce are investigated. Based on the geodesic analysis, we determine the upper and lower limits of critical impact parameters of a charged black-bounce. In particular, we find that the charged black-bounce shares the same critical impact parameter with the Reissner-Nordström black hole. In addition, we classify the light trajectories coming from the region near the charged black-bounce by utilizing the rays tracing procedure, and then investigate the observational appearance of the emissions from a thin disk accretion and a spherically symmetric infalling accretion. We reveal that a large charge increases the observed intensity but decreases the apparent size of shadows, and that the photon ring presents the intrinsic property of a spacetime geometry, which is independent of the types of the two accretions. Our results are in good agreement with the recent observations.