Probing a regular black hole within asymptotically safe gravity via strong gravitational lensings and optical appearances

Abstract

In this paper, we investigate the strong gravitational lensing effects and optical appearances around a spherically symmetric regular black hole, whose metric is derived from a non-singular collapsing dust ball model in asymptotically safe gravity. In this regular black hole spacetime, we obtain the analytical expression of the light deflection angle via calculating the strong field limit coefficients, and evaluate the lensing observables in strong field regime by supposing the regular black hole as the candidate of $M87^*$ and $SgrA^*$ supermassive black holes, respectively. Then, we study the optical appearances of an optically and geometrically thin spherical accretion around the regular black hole in this framework. Finally, we compare above results and show how much they differ from those obtained in the Schwarzschild black hole spacetime. We expect our results will be useful in the future to distinguish these non-singular black holes from their classical singular counterparts.

Figures (16)

• Figure 1: The radius of the photon sphere $r_m$ as a function of the scale parameter $\xi$.
• Figure 2: The critical impact parameter $b_m$ as a function of the scale parameter $\xi$.
• Figure 3: The strong field limit coefficient $\bar{a}$ as a function of the $\xi$.
• Figure 4: The strong field limit coefficient $\bar{b}$ as a function of the $\xi$.
• Figure 5: The strong deflection angle $\hat{\alpha}_{\xi}(b)$ as a function of the impact parameter $b$ for different values of the $\xi$.