Connections between the shadow radius and the quasinormal modes of Kerr-Sen black hole

Understand

The correspondence between the shadow radius and the quasi-normal modes of the Kerr-Sen black hole is studied.

• By using the equation of the shadow radius of the Kerr-Sen black hole and the angular separation constant of the quasi-normal modes, the expression of the real part of quasi-normal modes related to the shadow radius is obtained.
• We found that in the eikonal limit, our formula coincides with the previous result.
• Moreover, we also calculate the energy emission rate of the Kerr-Sen black hole, it turns out that the peak energy emissivity is inversely correlated with the charge parameter.