8th HEAD Meeting, 8-11 September, 2004
Session 7 Gravitational Astrophysics
Poster, Wednesday, September 8, 2004, 9:00am-10:00pm

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[7.01] Nonlinear Development of the Secular Bar-mode Instability in Rotating Neutron Stars

S. Ou, J. E. Tohline (Louisiana State University), L. Lindblom (Caltech)

We have modelled the nonlinear development of the secular bar-mode instability that is driven by gravitational radiation-reaction (GRR) forces in rotating neutron stars. In the absence of any competing viscous effects, an initially uniformly rotating, axisymmetric n=0.5 polytropic star with a ratio of rotational to gravitational potential energy T/|W|=0.181, which is secularly unstable but dynamically stable to the bar-mode instability, is driven by GRR forces to a bar-like structure, as predicted by linear theory. The pattern frequency of the bar slows to nearly zero, that is, the bar becomes almost stationary as viewed from an inertial frame of reference as GRR removes energy and angular momentum from the star. In this ``Dedekind-like'' state, rotational energy is stored as motion of the fluid in highly noncircular orbits inside the bar. However, this Dedekind-like bar configuration is dynamically unstable. In less than 10 dynamical times after its formation, the bar loses its initially coherent structure as the ordered flow inside the bar is disrupted by what appears to be a purely hydrodynamical, short-wavelength, ``shearing'' type instability. These results suggest that long-lived Dedekind-like objects are unlikely to be found in the universe. The gravitational waveforms generated by such an event are determined, and an estimate of the detectability of these waves is presented.

The author(s) of this abstract have provided an email address for comments about the abstract: ou@baton.phys.lsu.edu

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.