Strong gravitational lensing by Bardeen black holes in 4D EGB gravity: constraints from supermassive black holes

Understand

Observation indicates that many nearby galaxies host supermassive central black holes.

• Modelling Bardeen models in four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity, with additional parameters $\tilde{\alpha}$ and charge $q$, as central black holes in various galaxies, we investigate gravitational lensing properties in strong deflection limits.
• Interestingly, the spherical photon orbit radius $x_m$, the critical impact parameter $u_m$, the lensing coefficient $\bar{b}$, the deflection angle $\alpha_D(\theta)$, angular position $\theta_{\infty}$ are decreasing with $q$ and $\alpha$ whereas the other lensing coefficient $\bar{a}$ and angular separation $s$ have opposite behaviour.
• Taking the supermassive black holes Sgr A* and M87* as the lens, we also compare observable signatures of 4D EGB Bardeen black holes with those of the Schwarzschild black holes.