  Magnetic flares and induced oscillations of magnetars (super-magnetized
neutron stars) are promising sources of gravitational waves (GWs). We suggest
that the GW emission, if any, would last longer than the observed X-ray
quasi-periodic oscillations (X-QPOs), calling for the longer-term GW analyses
from a day to months than the current searches. Like the pulsar timing, the
oscillation frequency would also evolve with time because of the decay or
reconfiguration of magnetic field, which is crucial for the GW detection. With
the observed GW frequency and its time-derivatives, we can probe the interior
magnetic field strength and its evolution to open a new GW asteroseismology
with the next generation interferometers like advanced LIGO, advanced VIRGO,
LCGT and ET.
