  Soft Gamma Repeaters and the Anomalous X-ray Pulsars are believed to contain
slowly spinning "magnetars". The enormous energy liberated in the 2004 Dece 27
giant flare from SGR 1806-20, together with the likely recurrence time of such
events, points to an internal magnetic field strength ~ 10^{16} G. Such strong
fields are expected to be generated by a coherent alpha-Omega dynamo in the
early seconds after the Neutron Star formation, if its spin period is of a few
milliseconds at most. A substantial deformation of the NS is caused by such
fields and a newborn millisecond-spinning magnetar would thus radiate for a few
days a strong gravitational wave signal. Such a signal may be detected with
Advanced LIGO-class detectors up to the distance of the Virgo cluster, where ~
1 magnetar per year are expected to form. Recent X-ray observations reveal that
SNRs around magnetar candidates do not show evidence for a larger energy
content than standard SNRs (Vink & Kuiper 2006). This is at variance with what
would be expected if the spin energy of the young, millisecond NS were radiated
away as electromagnetic radiation andd/or relativistic particle winds and,
thus, transferred quickly to the expanding gas shell. We show here that these
recent findings can be reconciled with the idea of magnetars being formed with
fast spins, if most of their initial spin energy is radiated thorugh GWs. In
particular, we find that this occurs for essentially the same parameter range
that would make such objects detectable by Advanced LIGO-class detectors up to
the Virgo Cluster.
