Nonradial oscillations of neutron stars with the superfluid core.
Abstract
We investigate the nonradial oscillations of neutron stars with the superfluid core. We consider a most simplified case for the oscillations, ignoring the rotation and electromagnetic fields of the neutron stars. The core is assumed to be filled with free neutrons, protons, and electrons. All of the neutrons and protons are assumed to be in superfluid states and the normal components of the neutron and proton fluids are ignored since the transition temperatures are much higher than the interior temperature of neutron stars. We employ Newtonian hydrodynamic and hydrostatic equations to obtain wave solutions and equilibrium models for the neutron stars. The neutron star model is divided into the superfluid core and the normal fluid envelope. Different wave equations are integrated in the core and in the envelope, and a complete solution of the oscillation is obtained by applying jump conditions at the boundary between the core and envelope of the star. We find a class of modes associated with the superfluid core. We also find another class of modes which correspond to the f and p modes of a normal fluid star. This class of modes are not sensitive to superfluidity of the fluids in the core. The modes associated with the superfluid core are found among the f and p modes. Assuming composition gradient of the matter in local β equilibrium, we calculate low frequency g modes propagating in the interior of the neutron star. We find that superfluidity in the core inhibits the propagation of the g modes even if there exists the composition gradient.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 November 1995
 Bibcode:
 1995A&A...303..515L
 Keywords:

 STARS: NEUTRON;
 OSCILLATIONS;
 DENSE MATTER