First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform

We perform a wide parameter space search for continuous gravitational waves over the whole sky and over a large range of values of the frequency and the first spin-down parameter. Our search method is based on the Hough transform, which is a semi-coherent, computationally efficient, and robust pattern recognition technique. We apply this technique to data from the second science run of the LIGO detectors and our final results are all-sky upper limits on the strength of gravitational waves emitted by unknown isolated spinning neutron stars on a set of narrow frequency bands in the range 200-$400 $Hz. The best upper limit on the gravitational wave strain amplitude that we obtain in this frequency range is $4.43\times 10^{-23}$.