We discuss the modal properties of the r modes of relativistic superfluid neutron stars, taking account of the entrainment effects between superfluids. In this paper, the neutron stars are assumed to be filled with neutron and proton superfluids and the strength of the entrainment effects between the superfluids are represented by a single parameter η. We find that the basic properties of the r modes in a relativistic superfluid star are very similar to those found for a Newtonian superfluid star. The r modes of a relativistic superfluid star are split into two families: ordinary fluid-like r modes (ro mode) and superfiuid-like r modes (rs mode). The two superfluids counter-move for the rs modes, while they co-move for the r o modes. For the ro modes, the quantity κ ≡σ/Ω + m is almost independent of the entrainment parameter η, where m and σ are the azimuthal wave number and the oscillation frequency observed by an inertial observer at spatial infinity, respectively. For the rs modes, on the other hand, κ almost linearly increases with increasing η. It is also found that the radiation driven instability due to the rs modes is much weaker than that of the ro modes because the matter current associated with the axial parity perturbations almost completely vanishes.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)