  Tidal Disruption Events (TDEs) can be perfect probes of dormant SMBHs in
normal galaxies. During the rising phase, the accretion luminosity can increase
by orders of magnitude in several weeks and the emergent ionizing radiation
illuminates the fresh accretion flow. In this paper, we simulated the evolution
of the expected spectral line profile of iron due to such a flare by using a
ray-tracing code with effects of general relativity (GR) taken into account. We
found that the time-dependent profile changes significantly with black hole
spin, inclination angle with respect to the black-hole equatorial plane, and
the expansion velocity of the ionization front. At low values of spin, a "loop"
feature appears in the line profile vs. time plot when the inclination is no
less than $30^\circ$ and the expansion velocity $v_{\rm exp}$ is no less than
half speed of light, due to a shadow in the emission of the truncated disk. In
the light curve two peaks occur depending on the inclination angle. At large
$v_{\rm exp}$, a shallow "nose" feature may develop ahead of the loop, its
duration depends on the expansion velocity and the inclination angle. We
explore the entire interval of black hole spin parameter ranging from extreme
prograde to extreme retrograde rotation, $-1<a<1$. In the prograde case, a
low-energy tail appears to be more pronounced in the evolving centroid energy
of the line. Our results demonstrate the importance to search for X-ray
spectral lines in the early phase of TDE flares in order to constrain black
hole mass and spin, as well as properties of the innermost accretion flow.
