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R.V. Wagoner (Dept. of Physics, Stanford University)
The gravitational-wave and accretion driven evolution of the angular velocity, core temperature, and (small) amplitude of an r-mode of neutron stars in low mass X-ray binaries (LMXBs) and similar systems is investigated. The conditions required for evolution to a stable equilibrium state (with gravitational wave flux proportional to average X-ray flux) are determined. In keeping with conclusions derived from observations of cooling neutron stars, the core neutrons are taken to be normal while the core protons and hyperons and the crust neutrons are taken to be singlet superfluids. The dominant sources of damping are then hyperon bulk viscosity (if much of the core is at least 2-3 times nuclear density) and shear (and possibly magnetic) viscosity within the core-crust boundary layer. It is found that a stable equilibrium state can be reached if the superfluid transition temperature of the hyperons is sufficiently small, allowing the gravitational radiation from Sco X-1 and several other neutron stars in LMXBs to be potentially detectable by the Advanced LIGO (and VIRGO) arrays. As Brown & Ushomirsky (2000) have shown, observations of the luminosity of neutron star LMXBs in their quiescent phase constrain the r-mode amplitude if they have reached the equilibrium state we have considered. There is also a critical need for observational determinations of the spin periods of the candidate (X-ray brightest) neutron stars. This work was supported by NSF grant PHY-0070935.
The author(s) of this abstract have provided an email address for comments about the abstract: wagoner@stanford.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.