Strong gravitational lensing by Kerr-Sen dilaton-axion black hole

In the present work we study strong field limit, quasi-equatorial lensing by the charged, stationary, axially-symmetric Kerr-Sen dilaton-axion black hole. The most outstanding effect is that the Kerr-Sen black hole caustics drift away from the optical axis and shift in clockwise direction. The intersections of the critical curves on the equatorial plane as a function of the black hole angular momentum are found and it is showed that they decrease with the metric parameter Q2 / M. The magnifying power of the lens is shown.