  Detection of gravitational waves (GWs) paves the beginning of a new era of
gravitational wave astronomy. Black holes (BHs) in their ringdown phase provide
the cleanest signal of emitted GWs that imprint the fundamental nature of BHs
under low energy perturbation. Apart from GWs, any complementary signature of
ringing BHs can be of paramount importance. Motivated by this we analyzed the
scattering of electromagnetic waves in such a background and demonstrated that
the absorption cross section of a ringing Schwarzschild BH can be superradiant.
Moreover, we have found out that such superradiant phenomena are transient in
nature with a characteristic time scale equal to the GW oscillation time scale.
We further point out that the existing ground-based Low Frequency Array
(LOFAR), radio telescopes, may be able to detect such transient signals from
BHs of mass range $M\sim 10^{-1} - 10^{-2} M_{\odot}$, which should necessarily
be of primordial origin. Our present result opens up an intriguing possibility
of observing the black hole merging phenomena through electromagnetic waves.
