Nonradial oscillations of a neutron star in an inhomogeneous hydrodynamic model |
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| Authors: | D V Podgainyi S I Bastrukov I V Molodtsova V V Papoyan |
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| Institution: | (1) Saratov State University, Russia;(2) Joint Institute for Nuclear Research, Dubna, Russia;(3) Erevan State University, Armenia |
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| Abstract: | An inhomogeneous model neutron star with a variable density profile of the type  0(r)=c1–(2/3) r2/R2]exp(–r2/R2) is considered, where c is the central density, R is the star's radius, and is the inhomogeneity parameter in the radial mass distribution. This parameterization adequately reproduces the results of numerical evolutionary calculations of the density profile and enables one to obtain in analytical form the parameters of hydrostatic equilibrium and the eigenmodes of nonradial oscillations of a nonrotating neutron star, modeled by a spherical mass of incompressible, inviscid liquid. It is shown that a characteristic manifestation of the star's inhomogeneity is the presence of a stable dipole f-mode, the lowest one in the spectrum of natural oscillations. The presence of this mode serves as a general and primary criterion that evidently distinguishes all inhomogeneous hydrodynamic models from the homogeneous Kelvin model, in which the quadrupole mode is the lowest stable mode. Estimates obtained for the periods of nonradial pulsations coincide with the periods of micropulses observed in the average pulse profiles of c-pulsars. This suggests that the detected variations in emission intensity in the range of micropulse duration (on the order of 10–4 sec) are associated with nonradial stellar oscillations.Translated from Astrofizika, Vol. 39, No. 3, pp. 475–488, July–September, 1996. |
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