Quasiequatorial gravitational lensing by spinning black holes in the strong field limit

Abstract

Spherically symmetric black holes produce, by strong field lensing, two infinite series of relativistic images, formed by light rays winding around the black hole at distances comparable to the gravitational radius. In this paper, we address the relevance of the black hole spin for the strong field lensing phenomenology, focusing on trajectories close to the equatorial plane for simplicity. In this approximation, we derive a two-dimensional lens equation and formulae for the position and the magnification of the relativistic images in the strong field limit. The most outstanding effect is the generation of a non trivial caustic structure. Caustics drift away from the optical axis and acquire finite extension. For a high enough black hole spin, depending on the source extension, we can practically observe only one image rather than two infinite series of relativistic images. In this regime, additional non equatorial images may play an important role in the phenomenology.

Time Delay in Black Hole Gravitational Lensing as a Distance Estimator

“…In this case only one image at a time can be enhanced while all others stay very faint [17]. Nevertheless, in this case, additional images, appearing when the source is inside a caustic, may play an important role in the phenomenology, yet to be understood.…”

“…We treat only black holes with spherical symmetry, because only in this case we have the formation at first of more than one observable image. In fact, as noted in [17], the phenomenology of spinning black holes is quite different. In particular, if the source is not inside a caustic, only one image should become visible, while all the others stay very faint.…”

“…We shall briefly recall the main steps of that derivation referring the reader to Refs. [15,17] for all the details.…”

Kerr-Sen dilaton-axion black hole lensing in the strong deflection limit

“…Motivation for such a study in the SDL phenomenology comes from the fact that previous works on the subject have selected the supermassive black hole hosted by the radio source Sgr A* [37,38] as the best candidate for strong field gravitational lensing as it is mentioned in Ref. [46]. Unfortunately, in the first work approximations valid only for small deviations from the straight line path are considered, and therefore the proposed methods are not suited for studying relativistic images [39,40].…”

Strong Gravitational Lensing in the Einstein-Proca Theory

“…Also, the Kerr black hole pierced by a cosmic string has been studied with the same way by Wei et al [11]. With this method, lots of work in strong gravitational lensing has been studied, and the similar results are obtained [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]31]. However, the research of the gravitational lensing remained need us to continue perfecting it.…”