Gravitational radiation from highly magnetized nascent neutron stars in supernova remnants

We consider the spin evolution of highly magnetized neutron stars in a hypercritical inflow just after their birth in supernovae. Presence of a strong magnetic field could deform the star and if the symmetry axis of the field is misaligned with that of stellar rotation, the star will be an emitter of gravitational wave. Here we investigate the possibility of gravitational radiation from such a star when there is a hypercritical inflow onto it. For doing this we adopt a simplified model of the system in which the star is approximated as a Newtonian spherical polytrope with index N = 1. The stellar configuration is slightly deformed away from spherical by the intense magnetic field; the rotational angular frequency of the star is determined by the balance between the accretion torque and the magnetic dipole radiation. We take into account the ’propeller’ process in which a rotating stellar magnetic field flings away in-falling matter; the inflow is assumed to be a self-similar advection dominated flow. An estimation of the characteristic amplitude of the gravitational radiation from such systems is given. The computation of the signal-to-noise ratio suggests that for the case of an initially rapidly rotating and highly magnetized star (surface field 10G) in the Virgo Cluster, its ellipticity would need to be larger than 10 in order for the gravitational waves to be observed.