Identifications of quasi-periodic oscillations observed in soft-gamma repeaters with crustal torsional oscillations

Abstract

The quasi-periodic oscillations discovered in soft-gamma repeaters are considered due to the phenomena strongly associated with the oscillations of central objects, i.e., the neutron star oscillations. In order to explain the frequencies of the observed quasiperiodic oscillations, we focus on the crustal torsional oscillations in neutron stars, where we also take into account the effect of electron screening. Then, we are successful to constrain the density dependence of the nuclear symmetry energy (L), identifying the observed frequencies as the crust torsional oscillations with various angular indices.