Effect of superfluidity on neutron star oscillations

We consider how superfluidity of dripped neutrons in the crust of a neutron star affects the frequencies of the crust's fundamental torsional oscillations. Anon-negligible superfluid part of dripped neutrons, which do not comove with nuclei, acts to reduce the enthalpy density and thus enhance the oscillation frequencies. By assuming that the quasi-periodic oscillations observed in giant flares of soft gammarepeaters arise from the fundamental torsional oscillations and that the mass and radius of the neutron star are in the range 1.4 <= M/M-circle dot <= 1.8 and 10 <= R <= 14 km, we constrain the density derivative of the symmetry energy as 100 less than or similar to L less than or similar to 130 MeV, which is far more severe than the previous one, L greater than or similar to 50 MeV, derived by ignoring the superfluidity.