r-Mode Instability Of Neutron Stars: Surprise and Speculation

Several recent surprises appear dramatically to have improved the
likelihood that the spin of rapidly rotating, newly formed neutron
stars (and, possibly, of old stars spun up by accretion) is limited by
an instability driven by gravitational waves. If so, the emitted waves
may be observable by gravitational-wave detectors with the sensitivity
of LIGO II.  Although several possible ways to kill the instability have 
been suggested, it has so far survived them all.