Bulg. J. Phys. vol.38 no.1 (2011), pp. 113-122

Weak Gravitational Lensing by Rotating Dilaton-Axion Black Holes

G. Gyulchev1, S. Yazadjiev2
1Department of Physics, Biophysics and Roentgenology, Faculty of Medicine, University of Sofia, 1 Kozyak Str., 1407 Sofia, Bulgaria
2Department of Theoretical Physics, Faculty of Physics, University of Sofia, 5 James Bourchier Boulevard, 1164 Sofia, Bulgaria
Abstract. We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the light-like equations of motion are present up to and including third-order terms in M/b, a/b and rα/b, where M is the black hole mass, a is the angular momentum, rα=Q2/M, Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

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