Null geodesics and observables around the Kerr–Sen black hole

Abstract

Abstract. We investigate the geodesic motion in the background of Kerr-Sen Black Hole arising in the heterotic string theory. The nature of effective potential is discussed in radial as well as latitudinal direction. A special class of spherical photon orbits is obtained along with the expression for the turning point for radial photons. Dependence of photon motion within this class of solution is discussed explicitly in view of the different Black Hole parameters. We have discussed the allowed regions for geodesic motion of massless test particles around KerrSen Black Hole in more generalised way by including non-equatorial motion of the photons into the account. The conditions for different types of possible orbits are discussed with specific parameter values along with the corresponding orbit structure. No terminating orbits are possible for photons due to non-zero Black Hole charge. Observables on the angular plane (viz. bending of light and perihelion precession for massive test particles) are analysed as special cases. We have also calculated the rotation and mass parameters for Kerr-Sen Black Hole in terms of the red/blue shifts of the photons in circular and equatorial orbits emitted by the massive test particles which represent stars or other probable sources of photons.

Testing general relativity with x-ray reflection spectroscopy: The Konoplya-Rezzolla-Zhidenko parametrization

“…Non-Kerr metrics can be classified in two categories. The top-down metrics are those which are obtained as a solution of an alternative theory of gravity, e.g., the Einstein-dilaton-Gauss-Bonnet BHs [37][38][39][40][41][42], the Chern-Simons BHs [43][44][45][46], and the Kerr-Sen BHs [47][48][49][50]. The bottom-up metrics on the other hand are obtained not from a specific theory of gravity but by generalizing the Kerr metric [28,29,31,36,51].…”

Merger estimates for Kerr-Sen black holes

“…The correspondingṫ andφ in (3.15) and (3.16) are those of the null geodesic, i.e. 18) and the V eff is given in (3.12).…”

Kerr–Sen–Taub–NUT spacetime and circular geodesics

“…Recently, the author of [7] employ the same method to obtain the acccelerating spacetime in the low energy limit of heterotic string using the C-metric as the seed solution. Interestingly, aspects of black holes in the low energy limit of heterotic string theory have been studied quite comprehensively in literature [8][9][10][11][12][13][14][15][16].…”