All-Sky LIGO Search for Periodic Gravitational Waves in the Early Fifth-Science-Run Data

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50–1100 Hz and with the frequency’s time derivative in the range $-5\times {10}^{-9}–0\mathrm{Hz}{\mathrm{s}}^{-1}$. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below ${10}^{-24}$ are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of ${10}^{-6}$, the search is sensitive to distances as great as 500 pc.

Figure 1

Minimum (H1 or L1) upper limits (95% C.L.) on pulsar gravitational-wave amplitude $h_0$ for the equatorial (red), intermediate (green), and polar (blue) declination bands for best-case (lower curves) and worst-case (upper curves) pulsar orientations. Shown are all the minimum limits for each of the 11 spin-down values from $-5\times {10}^{-9}\mathrm{Hz}{\mathrm{s}}^{-1}$ to zero in steps of $5\times {10}^{-10}\mathrm{Hz}{\mathrm{s}}^{-1}$.