Nonradial oscillations of neutron stars

Finite-temperature neutron star models with a fluid core, solid crust, and thin surface fluid "ocean" are capable of sustaining a broad diversity of normal modes of oscillation. The authors have performed linear, adiabatic, Newtonian, nonradial pulsation analyses of such stars, including the elastic effects of the neutron star crust. Both spheroidal modes and toroidal modes are studied. Spheroidal modes, comprise p-, f-, and g-modes, well known from conventional stellar pulsation theory. For neutron stars, two additional classes of modes, termed s- and i-modes result from crustal elasticity and are relatively new to stellar astrophysics. The toroidal oscillations of neutron stars consist of torsional oscillations, which are normal modes of elastic waves in the solid crust. The authors suggest that surface g-modes may be excited during thermonuclear outbursts in X-ray bursters and may lead to observable quasi-periodic oscillations.