Effects of finite sizes of atomic nuclei on shear modulus and torsional oscillations in neutron stars

Abstract

ABSTRACT The shear modulus of neutron star matter is one of the important properties used for determining torsional oscillations in neutron stars. We take into account the effects of finite sizes of spherical nuclei on the shear modulus and examine the frequencies of crustal torsional oscillations. The shear modulus decreases owing to the finite-size effect, which in turn decreases the frequencies of torsional oscillations. In particular, the finite-size effect becomes more crucial for oscillations with a larger azimuthal quantum number and for neutron star models with a weaker density dependence of nuclear symmetry energy. In practice, when one identifies quasi-periodic oscillations from a neutron star, where magnetic effects are negligible, with crustal torsional oscillations, the finite-size effect can be more significant at frequencies higher than ∼100 Hz.