Perturbation of spacetime and electromagnetic field due to massive charged particle around electrically charged stringy black hole

This study investigates properties of static, electrically charged black hole within string theory using the non-rotating case of the Kerr–Sen solution. We derive the equilibrium condition for a test particle outside the black hole and examine perturbations via the combined Einstein–Maxwell equations. We extend the analysis to the extreme case, where the black hole’s electric charge reaches \(\sqrt{2}\) times of its mass. Formulating and solving perturbation equations for both extreme and non-extreme cases, we obtain and graph numerical solutions for the perturbation function L(r) in comparison with the standard Reissner–Nordström solution. We show that these two solutions behave identically at large distances, starting from the orbit of the perturbing source. Considerable difference can be observed only in the region between this orbit and the central black hole. These results provide insights into the influence of source mass and electric charge on perturbation behavior, contributing to our understanding of charged stringy black holes and paving the way for further investigations into their stability.