Strong gravitational lensing effects around rotating regular black holes

TL;DR

This paper studies how strong gravitational lensing around rotating regular black holes differs from Kerr black holes, analyzing observable effects like image positions and time delays, with implications for future telescope observations.

Contribution

It introduces analysis of lensing effects around rotating regular black holes and evaluates their observable differences from Kerr black holes using astrophysical data.

Findings

Time delay differences are potentially measurable with current or future telescopes.

Deviations in relativistic images are less than 10 microarcseconds, challenging current detection.

Regular black holes produce distinct lensing signatures compared to Kerr black holes.

Abstract

In this letter, we investigate the strong gravitational lensing effects around two classes of rotating regular black holes, which behave as non-singular Minkowski core at the center. Starting from the null geodesic in the equatorial plane of the regular black holes, we analyze the deflection angle for both prograde photons and retrograde photons, which are found to significantly shift from that for Kerr black hole. Then we suppose the rotating regular black holes as the supermassive M87* and SgrA* black holes, respectively, and evaluate the lensing observables such as the image position, separation, magnification and the time delays between the relativistic images for the black holes. In both cases, the time delay differences between the regular black holes and Kerr black hole seem to be measurable, especially for the M87* black hole, but the deviations of outermost relativistic image and the asymptotic relativistic image for the two rotating regular black holes from those for Kerr black hole are less than 10 $\mu as$. This means that it is difficult to probe the regularity of the black hole via the current observations, but we can expect the next generation Event Horizon Telescope to test more precise properties of strong field regime.