A frequency Comb Search for Sco X-1

We evaluate critically a semi-coherent gravitational wave search technique for continuous wave sources in binary systems, a technique called the frequency comb. The comb search is sensitive to the frequency and amplitude modulations produced by the orbital motion of the binary and the rotation of the earth, which generate sidebands in the detection statistic. It is implemented by summing incoherently the standard F-statistic, evaluated at each of these sidebands, with suitable weights. The sensitivity of the search is quantified with the aid of simulations on synthetic noisy data, and the results are compared with analytic estimates. The comb search is best suited to binaries with known sky position but unknown frequency, such as low mass x-ray binaries. Sco X-1, the brightest x-ray source in the sky, is a good candidate of this kind. Indirect limits on the signal from Sco X-1, e.g. from Bildsten's stalling hypothesis, are revised to include new effects related to the nuclear equation of state, surface magnetic geometry, and the accretion disk-magnetosphere interaction.