Triaxial neutron stars -- a possible source of gravitational radiation

Abstract

Triaxial neutron stars may be important sources of gravitational radiation for the forthcoming generation of interferometric gravitational wave detectors such as LIGO, VIRGO, and GEO600. We investigate the viscosity triggered bar mode secular instability of rapidly rotating neutron stars by means of a perturbation analysis of numerically constructed ``exact'' general relativistic axisymmetric star models. In the theoretical approach, only the dominant parts of the nonaxisymmetric terms of the 3D-Einstein equations are taken into account. A comparison of our results with previous studies of Newtonian polytropic stars confirms James' classical result gamma_crit=2.238 for the critical polytropic index. Beyond the Newtonian regime, gamma_crit reveals a slight increase toward highly relativistic configurations. Six out of twelve employed realistic dense matter equations of state admit the spontaneous symmetry breaking for masses above 1.6 M_sol.