Retrolensing by two photon spheres of a black-bounce spacetime

We investigate retrolensing by two photon spheres in a novel black-bounce spacetime suggested by Lobo et al. which can correspond to a Schwarzschild black hole, a regular black hole, and a traversable wormhole including an Ellis-Bronnikov wormhole. In a case, the wormhole has a throat which acts as a photon sphere and it has another photon sphere outside of the throat. With the sun as a light source, an observer, and the wormhole are lined up in this order, sunlight reflected slightly outside of the throat and barely outside and inside of the outer photon sphere can reach the observer. We show that the light rays reflected by the outer photon sphere are dominant in retrolensing light curves in the case.

Automated summary

This paper investigates retrolensing by two photon spheres in a novel black-bounce spacetime proposed by Lobo et al., which can correspond to different types of black holes and wormholes. In the case of a wormhole, there are two photon spheres inside and outside the wormhole, and the light rays reflected by these photon spheres can have an impact on the retrolensing light curves.