Abstract:

Rotating neutron stars have modes that are driven unstable by gravitational radiation reaction, principally the ``R-mode'', a Rossby wave with L=m=2, hence large gravitational radiation reaction. It has been suggested that the R-mode instability is what sets the largest angular frequency of rotation of accreting neutron stars. This maximum frequency depends on the neutron star composition via viscous dissipation and neutrino cooling, and so is a probe of the high density nuclear physics of neutron stars. The nonlinear development of the instability plays a very important role in determining how this process works, and also illustrates how instabilities can saturate at low amplitudes as a consequence of nearly resonant excitation of other modes. The saturation amplitude limits the prospects for detecting gravitational radiation from R-mode unstable neutron stars.