  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 Kerr- Sen 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.
