OSCILLATIONS OF ROTATING NEUTRON-STARS

We use a perturbation technique to compute the rotational corrections to the nonradial oscillation spectrum of a realistic neutron star model. We compute, to first-order in the rotation rate, the corrections to the normal mode eigenfrequencies and eigenfunctions. We find that l = l0 oscillations are coupled to l = l0 +/- 1 oscillations by the Coriolis force. To calculate the rotational corrections to the quadrupole, l0 = 2, oscillation modes we have extended previous calculations of the nonradial oscillation spectrum of this neutron star model to include l0 = 1 and l0 = 3 modes, as well as many higher overtones at each value of l0. As an example of this technique we have computed the rotational corrections to two quadrupole toroidal modes. For these modes the coupling to the spheroidal class of oscillations produced by the Coriolis force introduces a nonzero radial component to the velocity field, as well as a nonvanishing Lagrangian density perturbation. We use this result to compute the neutrino damping rates for these toroidal modes of a rotating neutron star. This mechanism does not damp the toroidal modes in a nonrotating star because these modes produce no density or temperature perturbations. We find that the neutrino damping time can approach the gravitational radiation damping time in rotating neutron stars if the central temperature is high enough, (T(c) greater-than-or-equal-to 10(8) K). The rotationally induced coupling of spheroidal oscillations to toroidal modes can also produce significant displacements at the stellar surface in some of the toroidal modes. This has important implications for the damping of these modes due to electromagnetic radiation. We have estimated the damping rates due to this process for the rotationally corrected toroidal modes. The coupling of surface motions to the toroidal modes also have interesting implications for channeling energy, e.g., that associated with a glitch in the crust, to the surface of the star. Perhaps this might produce observable effects in the pulsar emission process or a gamma-ray burst event.