Strong Gravitational Lensing by Compact Object without Cauchy Horizons in Effective Quantum Gravity

Abstract: In this work, we study strong gravitational lensing effects of a static, spherically symmetric solution in the context of effective quantum gravity (EQG). Among the three types of solutions proposed in EQG backgrounds, this is the third type without having Cauchy horizons. This solution gives rise to black hole as well as horizonless wormhole solutions depending on the range of values of the quantum parameter. Based on the data from SgrA* and M87* observations, possible bounds on the quantum parameter are obtained. It is found that the horizonless wormhole solutions are rule out by SgrA* observations but allowed by M87* observations. We analyze the lensing features of light in the strong deflection limit and evaluate various lensing observables both in the context of black hole and wormhole cases, and specifically study the effects of the quantum parameter on the them. It is shown that with increase of the quantum parameter, time delay between the first two relativistic images increases. Since its value comes out to be of the order of several days in the context of M87*, futuristic precision measurements of time delay may become important to specify parameters of background geometry more accurately.