2002/11/26 by Umin Lee, Shijun Yoshida · 1 citation
Engineering · Physics and Astronomy · #Dissipation #Dissipative system #Geophysics and Sensor Technology #Gravitational wave #Instability #Neutron #Neutron star #Oscillation (cell signaling) #Pulsars and Gravitational Waves Research #Scientific Research and Discoveries #Superfluidity #astro-ph #gr-qc
paper · pdf · doi:10.1086/367617
published as Astrophys.J.586:403,2003 · 22 pages, 22 figures, accepted for publication in the Astrophysical Journal
arxiv created 2002/11/26 · openalex publication_date 2003/03/20 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We investigate the modal properties of the r -modes of rotating neutron stars with the core filled with neutron and proton superfluids, taking account of entrainment effects between the superfluids. The stability of the r -modes against gravitational radiation reaction is also examined considering viscous dissipation due to shear and a damping mechanism called "mutual friction" between the superfluids in the core. We find that the r -modes in the superfluid core are split into ordinary r -modes and superfluid r -modes, which we call, respectively, r o - and r s -modes. The two superfluids in the core flow together for the r o -modes, while they countermove for the r s -modes. For the r o -modes, the coefficient κ 0 ≡ lim Ω→0 ω/Ω is equal to 2 m /[ l '( l ' + 1)], almost independent of the parameter η that parameterizes the entrainment effects between the superfluids, where Ω is the angular frequency of rotation, ω is the oscillation frequency observed in the corotating frame of the star, and l ' and m are the indices of the spherical harmonic function representing the angular dependence of the r -modes. For the r s -modes, on the other hand, κ 0 is equal to 2 m /[ l '( l ' + 1)] at η = 0 (no entrainment), and it almost linearly increases as η is increased from η = 0. The r o -modes, for which w ' ≡ v − v ∝ Ω 3 , correspond to the r -modes discussed by L. Lindblom & G. Mendell, where v and v are the Eulerian velocity perturbations of the neutron and proton superfluids, respectively. The mutual friction in the superfluid core is found ineffective to stabilize the r -mode instability caused by the r o -mode except in a few narrow regions of η. The r -mode instability caused by the r s -modes, on the other hand, is extremely weak and easily damped by dissipative processes in the star.