Oscillations of superfluid hyperon stars: decoupling scheme and g-modes

V. A. Dommes; M. E. Gusakov

doi:10.1093/mnras/stv2408

paper

Oscillations of superfluid hyperon stars: decoupling scheme and g-modes

arXiv:1512.04900 · doi:10.1093/mnras/stv2408

Abstract

We analyse the oscillations of general relativistic superfluid hyperon stars, following the approach suggested by Gusakov & Kantor and Gusakov et al. and generalizing it to the nucleon-hyperon matter. We show that the equations governing the oscillations can be split into two weakly coupled systems with the coupling parameters $s_{e}$ , $s_{μ}$ , and $s_{str}$ . The approximation $s_{e} = s_{μ} = s_{str} = 0$ (decoupling approximation) allows one to drastically simplify the calculations of stellar oscillation spectra. An efficiency of the presented scheme is illustrated by the calculation of sound speeds in the nucleon-hyperon matter composed of neutrons (n), protons (p), electrons (e), muons ( $μ$ ), as well as $Λ$ , $Ξ^{-}$ , and $Ξ^{0}$ -hyperons. However, the gravity oscillation modes (g-modes) cannot be treated within this approach, and we discuss them separately. For the first time we study the composition g-modes in superfluid hyperon stars with the $npe μ Λ$ core and show that there are two types of g-modes (`muonic' and ` $Λ$ --hyperonic') in such stars. We also calculate the g-mode spectrum and find out that the eigenfrequencies $ν$ of the superfluid g-modes can be exceptionally large (up to $ν \approx 742 Hz$ for a considered stellar model).

20 pages, 8 figures, published in MNRAS

Oscillations of superfluid hyperon stars: decoupling scheme and g-modes

Abstract

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